[INFRA] Publish schema tools API docs to additional ReadTheDocs site

[bendhouseart]

Read the docs now supports building documentation from mono repos, as such extra fluff and kludges previously required to publish a read the docs page for schema tools have been removed.

Rendered sites built of this branch can be viewed below:

schema tools rtd
bids rtd

Will need to update schema code project on RTD bids-standard/bids-specification and point to config file at tools/schemacode/.readthedocs.yaml to finalize after merge, see:

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (448e21e) 87.75% compared to head (fb83c33) 87.75%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1491   +/-   ##
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  Coverage   87.75%   87.75%           
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  Files          14       14           
  Lines        1282     1282           
=======================================
  Hits         1125     1125           
  Misses        157      157           

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[Remi-Gau]

Not sure that I understand what the requirements.txt is needed but as one your commit message says "what works work"

[bendhouseart]

Not sure that I understand what the requirements.txt is needed but as one your commit message says "what works works

RTD uses the project folder as the root and we (more or less) use the same dependencies for the bids spec generated on RTD as we do for schema-code docs. Now the config file for the schema docs more closely resembles bids-specificiation/readthedocs.yaml. I knew Chris was going to do a squash and merge so I wasn't the most clear with my commit messages, but what works is the original bids-specification/readthedocs.yaml ;)