Add support for ipywidgets on the server and in the notebook [doc-build]

[philippjfr]

This demonstrates bi-directional communication of an ipywidget embedded in a Panel/Bokeh layout in the notebook.

• Add docs
• Release jupyterlab_pyviz 1.1
• Try to support save and notebook exports somehow

Requires holoviz/pyviz_comms#57

[codecov]

Codecov Report

Merging #1285 into master will decrease coverage by 0.23%.
The diff coverage is 9.30%.

@@            Coverage Diff             @@
##           master    #1285      +/-   ##
==========================================
- Coverage   87.77%   87.53%   -0.24%     
==========================================
  Files         124      124              
  Lines       13480    13520      +40     
==========================================
+ Hits        11832    11835       +3     
- Misses       1648     1685      +37     

Impacted Files	Coverage Δ
panel/viewable.py	59.05% <9.30%> (-9.64%)	⬇️

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[MarcSkovMadsen]

Would users be able to specify IPyWidgets as widgets to panel.Param?

[MarcSkovMadsen]

Does this mean that users can use ipyleaflet, bqplot etc. with Panel? Or is it only the base IPyWidgets?

[philippjfr]

Does this mean that users can use ipyleaflet, bqplot etc. with Panel? Or is it only the base IPyWidgets?

It does indeed.

Would users be able to specify IPyWidgets as widgets to panel.Param?

Not yet, but possible in theory once this is merged.