Improvements for pyodide convert and doc builds

[philippjfr]

• Allows pyodide mime render code to capture stdout and stderr live
• Builds wheel with bundled contents during release and makes it available to convert and docs output via unpkg CDN

[codecov]

Codecov Report

Merging #3857 (1140411) into master (ae2fa3d) will decrease coverage by 0.00%.
The diff coverage is 70.68%.

@@            Coverage Diff             @@
##           master    #3857      +/-   ##
==========================================
- Coverage   82.94%   82.93%   -0.01%     
==========================================
  Files         224      224              
  Lines       32714    32740      +26     
==========================================
+ Hits        27133    27153      +20     
- Misses       5581     5587       +6     

Flag	Coverage Δ
ui-tests	34.38% <31.03%> (+0.01%)	⬆️
unitexamples-tests	75.16% <70.68%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
panel/io/pyodide.py	0.00% <0.00%> (ø)
panel/io/convert.py	30.80% <70.00%> (+1.36%)	⬆️
panel/util.py	87.08% <83.33%> (-0.09%)	⬇️
panel/io/mime_render.py	84.46% <100.00%> (+1.30%)	⬆️
panel/tests/io/test_mime_render.py	100.00% <100.00%> (ø)
panel/tests/util.py	87.37% <0.00%> (-0.98%)	⬇️
panel/io/state.py	69.15% <0.00%> (-0.20%)	⬇️

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