Support React 18 (#320)

An [exciting PR](storybookjs/storybook#17215) has been merged and released in `6.5.0-alpha.58 ` that adds storybook support for React 18.  However, it currently breaks in the vite-builder test because of an `import()` of the new `react-dom/client`, which only exists in react 18.  Due to vitejs/vite#6007, we have to do a little bit of trickery to stop vite from erroring out.  The approach I'm taking here is:

1) Rewriting the import of `react-dom/client` to a dummy file if it can't be `require.resolve()`ed.  This fixes the problem in production builds.
2) Additionally, adding `react-dom/client` to the list of `optimizeDeps.exclude` if the framework is react and the package can't be required.  This is necessary to prevent vite from trying to pre-bundle, and throwing errors in dev.

This PR also updates the examples to the new `6.5.0-alpha.58` version of storybook, which includes the PR mentioned above, so that it can be tested in our react examples, and it adds a new `react-18` example as well.

examples/react-18/.env

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+STORYBOOK_ENV_VAR=included
+VITE_ENV_VAR=included
+ENV_VAR=should_not_be_included

examples/react-18/.storybook/main.js

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+module.exports = {
+  framework: '@storybook/react',
+  stories: ['../stories/**/*.stories.mdx', '../stories/**/*.stories.@(js|jsx|ts|tsx)'],
+  addons: ['@storybook/addon-a11y', '@storybook/addon-links', '@storybook/addon-essentials'],
+  core: {
+    builder: '@storybook/builder-vite',
+  },
+  features: {
+    storyStoreV7: true,
+  },
+  async viteFinal(config, { configType }) {
+    // customize the Vite config here
+    return config;
+  },
+};

examples/react-18/.storybook/preview.js

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+export const parameters = {
+  actions: { argTypesRegex: '^on[A-Z].*' },
+  controls: {
+    matchers: {
+      color: /(background|color)$/i,
+      date: /Date$/,
+    },
+  },
+};

examples/react-18/package.json

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+{
+  "name": "example-react-18",
+  "private": true,
+  "version": "0.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "storybook": "start-storybook --port 6018",
+    "build-storybook": "build-storybook",
+    "preview-storybook": "http-server storybook-static --port 6018 --silent",
+    "test": "wait-on tcp:6018 && test-storybook --url 'http://localhost:6018'",
+    "test-ci": "run-p --race test preview-storybook"
+  },
+  "author": "",
+  "license": "MIT",
+  "dependencies": {
+    "react": "^18.0.0",
+    "react-dom": "^18.0.0"
+  },
+  "devDependencies": {
+    "@storybook/addon-a11y": "^6.5.0-alpha.58",
+    "@storybook/addon-docs": "^6.5.0-alpha.58",
+    "@storybook/addon-essentials": "^6.5.0-alpha.58",
+    "@storybook/builder-vite": "workspace:*",
+    "@storybook/react": "^6.5.0-alpha.58",
+    "@storybook/test-runner": "^0.0.4",
+    "@vitejs/plugin-react": "^1.3.0",
+    "http-server": "^14.1.0",
+    "jest": "^27.5.1",
+    "npm-run-all": "^4.1.5",
+    "vite": "2.9.0",
+    "wait-on": "^6.0.1"
+  }
+}

examples/react-18/stories/Button.jsx

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+import PropTypes from 'prop-types';
+import './button.css';
+
+/**
+ * Primary UI component for user interaction
+ */
+export const Button = ({ primary, backgroundColor, size, label, ...props }) => {
+  const mode = primary ? 'storybook-button--primary' : 'storybook-button--secondary';
+  return (
+    <button
+      type="button"
+      className={['storybook-button', `storybook-button--${size}`, mode].join(' ')}
+      style={backgroundColor && { backgroundColor }}
+      {...props}
+    >
+      {label}
+    </button>
+  );
+};
+
+Button.propTypes = {
+  /**
+   * Is this the principal call to action on the page?
+   */
+  primary: PropTypes.bool,
+  /**
+   * What background color to use
+   */
+  backgroundColor: PropTypes.string,
+  /**
+   * How large should the button be?
+   */
+  size: PropTypes.oneOf(['small', 'medium', 'large']),
+  /**
+   * Button contents
+   */
+  label: PropTypes.string.isRequired,
+  /**
+   * Optional click handler
+   */
+  onClick: PropTypes.func,
+};
+
+Button.defaultProps = {
+  backgroundColor: null,
+  primary: false,
+  size: 'medium',
+  onClick: undefined,
+};

examples/react-18/stories/Button.stories.jsx

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+import { Button } from './Button';
+
+export default {
+  // no title, to demonstrate autotitle
+  component: Button,
+  argTypes: {
+    backgroundColor: { control: 'color' },
+  },
+};
+
+export const Primary = {
+  args: {
+    primary: true,
+    label: 'Button',
+  },
+};
+
+export const Secondary = {
+  args: {
+    label: 'Button',
+  },
+};
+
+export const Large = {
+  args: {
+    size: 'large',
+    label: 'Button',
+  },
+};
+
+export const Small = {
+  args: {
+    size: 'small',
+    label: 'Button',
+  },
+};

examples/react-18/stories/EnvironmentVariables.jsx

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+export function EnvironmentVariables() {
+  return (
+    <div>
+      <h1>import . meta . env:</h1>
+      <div>{JSON.stringify(import.meta.env, null, 2)}</div>
+      <h1>import . meta . env . STORYBOOK:</h1>
+      <div>{import.meta.env.STORYBOOK}</div>
+      <h1>import . meta . env . STORYBOOK_ENV_VAR:</h1>
+      <div>{import.meta.env.STORYBOOK_ENV_VAR}</div>
+      <h1>import . meta . env . VITE_ENV_VAR:</h1>
+      <div>{import.meta.env.VITE_ENV_VAR}</div>
+      <h1>import . meta . env . ENV_VAR:</h1>
+      <div>{import.meta.env.ENV_VAR}</div>
+    </div>
+  );
+}

examples/react-18/stories/EnvironmentVariables.stories.jsx

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+import { EnvironmentVariables } from './EnvironmentVariables';
+
+export default {
+  title: 'Environment Variables',
+  component: EnvironmentVariables,
+};
+
+export const Info = () => <EnvironmentVariables />;

examples/react-18/stories/Header.jsx

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+import PropTypes from 'prop-types';
+
+import { Button } from './Button';
+import './header.css';
+
+export const Header = ({ user, onLogin, onLogout, onCreateAccount }) => (
+  <header>
+    <div className="wrapper">
+      <div>
+        <svg width="32" height="32" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
+          <g fill="none" fillRule="evenodd">
+            <path d="M10 0h12a10 10 0 0110 10v12a10 10 0 01-10 10H10A10 10 0 010 22V10A10 10 0 0110 0z" fill="#FFF" />
+            <path d="M5.3 10.6l10.4 6v11.1l-10.4-6v-11zm11.4-6.2l9.7 5.5-9.7 5.6V4.4z" fill="#555AB9" />
+            <path d="M27.2 10.6v11.2l-10.5 6V16.5l10.5-6zM15.7 4.4v11L6 10l9.7-5.5z" fill="#91BAF8" />
+          </g>
+        </svg>
+        <h1>Acme</h1>
+      </div>
+      <div>
+        {user ? (
+          <Button size="small" onClick={onLogout} label="Log out" />
+        ) : (
+          <>
+            <Button size="small" onClick={onLogin} label="Log in" />
+            <Button primary size="small" onClick={onCreateAccount} label="Sign up" />
+          </>
+        )}
+      </div>
+    </div>
+  </header>
+);
+
+Header.propTypes = {
+  user: PropTypes.shape({}),
+  onLogin: PropTypes.func.isRequired,
+  onLogout: PropTypes.func.isRequired,
+  onCreateAccount: PropTypes.func.isRequired,
+};
+
+Header.defaultProps = {
+  user: null,
+};

examples/react-18/stories/Header.stories.jsx

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+import { Header } from './Header';
+
+export default {
+  title: 'Example/Header',
+  component: Header,
+};
+
+const Template = (args) => <Header {...args} />;
+
+export const LoggedIn = Template.bind({});
+LoggedIn.args = {
+  user: {},
+};
+
+export const LoggedOut = Template.bind({});
+LoggedOut.args = {};