update doc dependencies, use furo theme

[ITProKyle]

Summary

Update Sphinx to the latest version we are able to given the python version requirement.
Replace sphinx_rtd_theme with furo, a dynamic theme supporting a light and dark mode used for some official python documentation.

• Existing documentation using sphinx_rtd_theme: https://runway.readthedocs.io/latest/
• Built from this PR: https://runway.readthedocs.io/docs-furo/

Why This Is Needed

Improved stability for building Runway's documentation and to provide a more modern look.

What Changed

Added

• added furo to the docs dependency group
• added sphinx-copybutton to the docs dependency group
• added sphinx-design to the docs dependency group
  • replaces sphinx-tabs
• added sphinx-notfound-page to the docs dependency group
• added sphinxcontrib-external-links to the docs dependency group
• added sphinxcontrib-jquery to the docs dependency group
  • used by a new JS script that causes external links to be opened in new browser windows

Changed

• updated docs dependency group

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.16%. Comparing base (26e72a7) to head (5b87182).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2507   +/-   ##
=======================================
  Coverage   90.16%   90.16%           
=======================================
  Files         247      247           
  Lines       15610    15610           
=======================================
  Hits        14074    14074           
  Misses       1536     1536           

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[alexander-kogan]

LGTM