[Tracking] Website Overhaul

[mowies]

Goal

We want to have a new website that is built on top of a new site generator that will make maintenance and setup of docs much simpler. Additionally, a new hosting provider should be used so that hosting of the website will be easier as well.

Details

After the initial research done in #2458, the plan is to move the docs to MkDocs and use the Material for MkDocs theme which comes with lots of extra features that take work off of the team's hands when it comes to customization of the website.
For hosting, ReadTheDocs will be used since it provides features that are tailored towards technical documentation which again, will make maintainability better.

Versioning of the website will be removed from the website for now since the project doesn't really need it except for certain specific pages like the Upgrade page.

PoC for this epic with a fully working setup: https://github.com/mowies/mkdocs-testing
The corresponding website can be accessed here: https://mkdocs-testing.readthedocs.io/en/stable/
The corresponding ReadTheDocs project can be accessed here: https://readthedocs.org/projects/mkdocs-testing/

Tasks

Preview Give feedback

1. Set up new page next to old docs with a placeholder index page #2550
   docs-infrastructure +1
   
2. Set up ReadTheDocs to build new docs page #2552
   docs-infrastructure +1
   
3. Copy content to new docs page #2553
   docs-infrastructure documentation +2
   
4. Create new landing page with custom theme #2548
   docs-infrastructure +1
   
5. Update makefiles to work with new docs engine #2555
   docs-infrastructure +1
   
6. Remove docs release pipeline #2551
   docs-infrastructure good first issue +2
   
7. Adapt DNS settings and Google search console settings for new page #2585
   docs-infrastructure +1
   
8. Update contribution guide with new content about local development and branches #2584
   documentation +1
   
9. Substitute code fragments with include shortcodes #2587
   documentation good first issue +2
10. Fill index pages with summaries of content inside the sections #2586
    documentation +1
    
11. Adapt versioning scheme for new docs page #2592
    docs-infrastructure +1
12. Listing here all new website setup actions I could not find in the backlog #2774
    docs-infrastructure documentation +2
    

[mowies]

Closing this since everything is done except for one issue, that will hopefully be done by the community