Improve meta tags in initial HTML response

[d-claassen]

Change the boilerplate HTML/response on https://ui-library.yoast.com. The current <title> and (lack of) metadata leave a lot to be desired.

There might be possibilities to improve this according to the documentation at https://storybook.js.org/docs/react/sharing/publish-storybook#search-engine-optimization-seo.

Storybook is by default configured to use Webpack 4 under the hood. In it's build process it uses the HtmlWebpackPlugin to generate the HTML template. That plugin uses this template file to generate the initial HTML response.