Fix Read The Docs

[kbourgoin]

...does what it says on the tin.

• Fixes RTD builds
• Renames the main testing workflow action to "Tests"
• Adds tests and docs build badges to the README
• Updates the release doc file to be reST and makes the formatting/language similar to other docs in the library

Fixes #456

[kbourgoin]

Hey @thornycrackers, @rachelannelise, or @lmontopo. I see you on #505 pretty recently. Mind giving this a quick gander? I fixed it to read the docs works again, as do the badges on the README.

I reformatted the recent entry a bit as well so that it builds correctly.

[thornycrackers]

I ran a build with PYTHONPATH=$(pwd) sphinx-build -M html ./doc ./dist and everything seemed out build correctly with no warnings so 👍