Add copy button to Markdown codeblocks

[philippjfr]

Implements #6209

[MarcSkovMadsen]

Would be so great for chat and many other use cases.

[ahuang11]

One feature that I really like about ChatGPT is how the "Copy Code" follows the scroll position, up to the end of the code, so users don't have to scroll all the way up to copy. Is it easy to implement that feature?

Screen.Recording.2024-10-30.at.9.24.55.AM.mov

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.24%. Comparing base (8dd362f) to head (30dd111).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7451      +/-   ##
==========================================
+ Coverage   82.08%   82.24%   +0.16%     
==========================================
  Files         337      337              
  Lines       50680    50680              
==========================================
+ Hits        41599    41684      +85     
+ Misses       9081     8996      -85     

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[Coderambling]

One feature that I really like about ChatGPT is how the "Copy Code" follows the scroll position, up to the end of the code, so users don't have to scroll all the way up to copy. Is it easy to implement that feature?

Screen.Recording.2024-10-30.at.9.24.55.AM.mov

If the "follow" functionality is tricky to implement, maybe simply put an instance of the copy button at the end of the code block, as well as the beginning? Would also be a little less busy than a "following" button.

[philippjfr]

Will skip the following behavior for now. Adding two buttons is definitely too busy.