Overhaul of ServiceX Docs for 3.0 release

[BenGalewsky]

• Major PR for the documentation of 3.0 client library
• This resolves docs: Add link back to GitHub repository from the documentation #446

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.92%. Comparing base (2dfb069) to head (2d248b1).
Report is 53 commits behind head on 3.0_develop.

Additional details and impacted files

@@               Coverage Diff               @@
##           3.0_develop     #444      +/-   ##
===============================================
+ Coverage        82.02%   82.92%   +0.90%     
===============================================
  Files               26       26              
  Lines             1363     1429      +66     
===============================================
+ Hits              1118     1185      +67     
+ Misses             245      244       -1     

Flag	Coverage Δ
unittests	82.92% <100.00%> (+0.90%)	⬆️

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[ketan96-m]

As a final step to merge to 3.0_develop, removing the doc_week entry from the docs.yml file.

[matthewfeickert]

These are formatting errors found quickly passing through that are in the changes made. There are others in the docs that aren't in files touch yet, so those should also get fixed.

[matthewfeickert]

Please use the Resolves #446 syntax in the body (currently blank) of this PR to close out the issue once this is merged. (#446 (comment))

As a follow up to this, and something that @ponyisi raised on Slack, in the 3.0_develop branch README (https://github.com/ssl-hep/ServiceX_frontend/blob/55d44f08eaae713747b25dcfca3f4910e731762a/README.md) there is no link to any docs in the README.

Please add a link to the ReadTheDocs (https://servicex-frontend.readthedocs.io/) — and maybe also to the dev docs on GitHub pages (https://ssl-hep.github.io/ServiceX_frontend/) — and make the ReadTheDocs versioned and point to stable by default (not latest).

[matthewfeickert]

• This resolves docs: Add link back to GitHub repository from the documentation #446

Just for future reference (doesn't matter here), putting text in front of Resolves #XXX breaks the operations. So it needs to literally be just

* Resolves #446