Porting documentation to Docusaurus

Created by: selbekk

Ref #5209 (closed), this issue will work as a base for planning the work of creating a Docusaurus documentation website for create-react-app.

Task list

An initial task overview might look like this:

• Initial setup of Docusaurus (@amyrlam / #5227)
• Removing the blog feature from Docusaurus (@selbekk / #5239)
• Removing sample content and pages (@selbekk / #5242)
• Updating the siteConfig.js file with correct names (@selbekk / #5243)
• Add favicons and og-images from the reactjs.org page (@selbekk / #5244)
• Set up basic documentation structure (@selbekk / #5245)
• Change the color scheme to something more React-y (@selbekk / #5249)
• Update footer links (@selbekk / #5251)
• Create an initial front page design (@selbekk / #5341)
• Create getting started docs (@selbekk / #5344)
• Create user guide docs (@selbekk / #5347)
• Split up user guide docs into sections (@selbekk / #5347)
• Set up Algolia search https://github.com/facebook/create-react-app/pull/5551
• Change the mobile navigation colors (@selbekk / #5398)
• Improve visibility of text links in docs (@selbekk / #5357)
• Add some more content to the landing page (@selbekk / #5398)
• Launch site on Github Pages (?)
• Update GitHub readmes etc to reference the website
• Decide what to do with the template README
• Update bit.ly/CRA-PWA link

This task list will be updated, edited and changed as we come up with more tasks, or split larger ones up into smaller ones.

Documentation structure

There are many ways of structuring the content found in this repo, but I think a good first approach is to split it into two parts:

• Getting started (some of the information from the README.md file can go here)
• User Guide (as is, for now)

From there, we can split it up into more narrow "groups", if we find it appropriate and helpful for the user.