feat: add babel and postcss configs to templates

lib/snowpacker/templates/babel.config.js

@@ -0,0 +1,72 @@
+module.exports = function() {
+  const validEnv = ['development', 'test', 'production']
+  const currentEnv = process.env["NODE_ENV"]
+  const isDevelopmentEnv = (currentEnv === "development")
+  const isProductionEnv = (currentEnv === 'production')
+  const isTestEnv = (currentEnv === 'test')
+
+  if (!validEnv.includes(currentEnv)) {
+    throw new Error(
+      'Please specify a valid `NODE_ENV` or ' +
+        '`BABEL_ENV` environment variables. Valid values are "development", ' +
+        '"test", and "production". Instead, received: ' +
+        JSON.stringify(currentEnv) +
+        '.'
+    )
+  }
+
+  return {
+    presets: [
+      isTestEnv && [
+        '@babel/preset-env',
+        {
+          targets: {
+            node: 'current'
+          }
+        }
+      ],
+      (isProductionEnv || isDevelopmentEnv) && [
+        '@babel/preset-env',
+        {
+          forceAllTransforms: true,
+          useBuiltIns: 'entry',
+          corejs: 3,
+          modules: false,
+          exclude: ['transform-typeof-symbol']
+        }
+      ]
+    ].filter(Boolean),
+    plugins: [
+      'babel-plugin-macros',
+      '@babel/plugin-syntax-dynamic-import',
+      isTestEnv && 'babel-plugin-dynamic-import-node',
+      '@babel/plugin-transform-destructuring',
+      [
+        '@babel/plugin-proposal-class-properties',
+        {
+          loose: true
+        }
+      ],
+      [
+        '@babel/plugin-proposal-object-rest-spread',
+        {
+          useBuiltIns: true
+        }
+      ],
+      [
+        '@babel/plugin-transform-runtime',
+        {
+          helpers: false,
+          regenerator: true,
+          corejs: false
+        }
+      ],
+      [
+        '@babel/plugin-transform-regenerator',
+        {
+          async: false
+        }
+      ]
+    ].filter(Boolean)
+  }
+}

lib/snowpacker/templates/postcss.config.js

@@ -0,0 +1,12 @@
+module.exports = {
+  plugins: [
+    require('postcss-import'),
+    require('postcss-flexbugs-fixes'),
+    require('postcss-preset-env')({
+      autoprefixer: {
+        flexbox: 'no-2009'
+      },
+      stage: 3
+    })
+  ]
+}