ENH: Adding scroll bars with proper cell tags

[dprada]

Some lines were added to mystnb.css to add scroll bars with tags: 'output_scroll', 'scroll-output' and 'scroll-input'.

The lines implemented are similar to the paragraph in https://github.com/executablebooks/sphinx-book-theme/blob/eb1b6baf098b27605e8f2b7b2979b17ebf1b9540/src/sphinx_book_theme/assets/styles/extensions/_myst-nb.scss#L21. The only difference is the inclusion of indications for horizontal bars (width and y lines).

See #453

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.63%. Comparing base (385c4a7) to head (0e94fca).
Report is 94 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #454      +/-   ##
==========================================
- Coverage   81.67%   81.63%   -0.04%     
==========================================
  Files          29       29              
  Lines        2647     2647              
==========================================
- Hits         2162     2161       -1     
- Misses        485      486       +1     

Flag	Coverage Δ
pytests	81.63% <ø> (-0.04%)	⬇️

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[chrisjsewell]

thanks @dprada have a look at my comment for changes

[dprada]

This was already solved, right?

[bsipocz]

Previous review comments have been addressed, and I've read through the xreffed discussions and think this should be a go ahead.

Thanks @dprada!

The review comments have been addressed.