Fix Tutorial Issues

[MarcSkovMadsen]

Closes #6611

• Addresses all of issues in Textual Reference Docs issues #6606 except that the docs are rendered with Pyodide. I would expect someone else to fix that.
• Adds "missing" crossfiltering dashboard. It is one of the things that Panel/ HoloViews uniquely does really well and easily.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.95%. Comparing base (d59b23b) to head (6236f67).
Report is 4 commits behind head on main.

❗ Current head 6236f67 differs from pull request most recent head 9d3df31. Consider uploading reports for the commit 9d3df31 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6614      +/-   ##
==========================================
+ Coverage   82.94%   82.95%   +0.01%     
==========================================
  Files         313      313              
  Lines       46090    46090              
==========================================
+ Hits        38231    38236       +5     
+ Misses       7859     7854       -5     

Flag	Coverage Δ
ui-tests	40.03% <ø> (ø)
unitexamples-tests	71.24% <ø> (+0.01%)	⬆️

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[philippjfr]

Would prefer keeping fixes separate from new PRs. I'm going to merge this without the new tutorial section.

[philippjfr]

Here's the new section, so it doesn't get lost:

build_crossfilter_dashboard.md

[philippjfr]

Thanks so much for these fixes!