Tweaks to documentation

[ffl096]

• Adds a link to the GitHub repository to the right of the documentation navbar.
• Replaces the doc source button with a more helpful edit button.
• Add "copy code" button to all examples.
• Add a standard code of conduct.

Depends on pyt-team/TopoNetX#392 (for the code of conduct).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.62%. Comparing base (95c4abf) to head (8c83d04).
Report is 16 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #56   +/-   ##
=======================================
  Coverage   96.62%   96.62%           
=======================================
  Files           8        8           
  Lines         178      178           
=======================================
  Hits          172      172           
  Misses          6        6           

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