Document Tabulator Styling with Matplotlib gradients

[MarcSkovMadsen]

One of the most used features in Excel is applying colormap gradients to your tables. You can do the same with Tabulator in Panel.

I've many times been searching for this and experienced some issues.

• How to do this is not documented.
• Often the gradients don't show. Its actually because I did not have Matplotlib installed. But its very hard to figure out because no warning or exception is displayed. I've spent countless hours trying to understand why it works locally but not when deployed. I thought Panel Tabulator Styling was a bit fragile depending on Pandas versions etc.

This PR makes it much easier for users to apply gradients to Tabulator by documenting an example and documenting Matplotlib requirement.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.79%. Comparing base (d4f7d68) to head (c7905dc).

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HEAD has 8 uploads less than BASE

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Additional details and impacted files

@@             Coverage Diff             @@
##             main    #7291       +/-   ##
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- Coverage   82.18%   71.79%   -10.40%     
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  Files         337      336        -1     
  Lines       50380    50379        -1     
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- Hits        41407    36169     -5238     
- Misses       8973    14210     +5237     

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