Adapt docs to MyST

[ErikDanielsson]

Converted documentation to MyST syntax, which will enable us to write the documentation in Markdown instead of reStructuredText. There is no support for writing docstrings in Markdown with MyST currently however, see the MyST docs. The we best can get currently is having the main part of the documentation written in Markdown and continue writing the docstrings in rst until the the sphinx autodocs module is flexible enough to support Markdown.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #1245 (348b105) into dev (d6ccdd7) will not change coverage.
The diff coverage is n/a.

❗ Current head 348b105 differs from pull request most recent head 9295189. Consider uploading reports for the commit 9295189 to get more accurate results

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  Coverage   64.81%   64.81%           
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  Files          51       51           
  Lines        6002     6002           
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  Hits         3890     3890           
  Misses       2112     2112           

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[ewels]

Wondering if we should just ditch Sphinx completely and use MkDocs with MkDocStrings

Might be cleaner, and then we can just use markdown everywhere.

[ewels]

Tested locally, seems to be working well now I added the myst-parser requirement 👍🏻

Still think it might be worth us moving to MkDocStrings for full markdown, but will take that after these PRs are merged (if at all..)