ReadTheDocs configuration file (v2)

[CasperWA]

Close #452

Move to ReadTheDocs. This PR adds a configuration file for it.

[codecov]

Codecov Report

Merging #485 (bca0ab1) into master (da20c54) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #485   +/-   ##
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  Coverage   92.20%   92.20%           
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  Files          61       61           
  Lines        3246     3246           
=======================================
  Hits         2993     2993           
  Misses        253      253           

Flag	Coverage Δ
project	92.20% <ø> (ø)
validator	65.89% <ø> (ø)

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[ml-evs]

What was the decision about whether we should go ahead with this @CasperWA? Could we enable it for this PR and see how well it works?

Pros:

• versioned docs
• doc previews on PR builds

Cons:

• Ads (fairly unobtrusive)
• Slightly less/more convoluted control over builds
• I don't think we'll get docs for older versions, unless we add the readthedocs config file and retag (disabling our PyPI release beforehand)

[ml-evs]

Could we enable it for this PR and see how well it works?

Just found that its already enabled (but not showing up in GitHub status checks), but the build is failing...

[ml-evs]

Could we enable it for this PR and see how well it works?

Just found that its already enabled (but not showing up in GitHub status checks), but the build is failing...

The PR build itself is fine, so it should work in master too. I'm happy to merge this so we can evaluate both options "live", then eventually sunset the mkdocs/pages build and switch the URL over to readthedocs. Your call @CasperWA.

[ml-evs]

Hmmm, master builds are still failing even after merging, due to an API reference error. I'll try to fix this before 0.12.5, otherwise we won't get any 0.12.x docs versions up.

Scratch that, stable != master 🤦