Improve Ipywidgets reference guide

[MarcSkovMadsen]

Working on developmentseed/lonboard#539 and reading the questions in developmentseed/lonboard#262 I released that the Ipywidgets reference guide does not explain fully how Panel supports ipywidgets.

This PR adds the missing explanations.

I've also found inspiration in the Shiny docs https://shiny.posit.co/py/docs/jupyter-widgets.html. Thanks to Shiny.

[philippjfr]

If you want to convert your ipywidget to a Panel native widget, you can do so with Panel's AnyWidgetComponent, JSComponent, or ReactComponent.

These links won't be correct, should be ../custom_components/....

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.54%. Comparing base (cdcd074) to head (883eb7b).
Report is 90 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6892       +/-   ##
===========================================
+ Coverage   22.10%   81.54%   +59.44%     
===========================================
  Files         314      319        +5     
  Lines       46326    46915      +589     
===========================================
+ Hits        10240    38259    +28019     
+ Misses      36086     8656    -27430     

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[MarcSkovMadsen]

If you want to convert your ipywidget to a Panel native widget, you can do so with Panel's AnyWidgetComponent, JSComponent, or ReactComponent.

These links won't be correct, should be ../custom_components/....

Thanks. Fixed.

[MarcSkovMadsen]

I changed the Sizing section to recommend fixing issues by settings widget.layout.width=widget.layout.height="100%". At least that works for ipyleaflet and lonboard. After that the IPyWidget pane can control the sizing.

I believe this is ready. Let me know if there is more I should do. Thanks.

[MarcSkovMadsen]

Super seeded by #6912