Misc, player and select docstrings

[MarcSkovMadsen]

Adds docstrings to the misc, player and select modules to improve the user experience when developing in an IDE.

[codecov]

Codecov Report

Merging #3366 (7c55fbf) into master (3504e87) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3366      +/-   ##
==========================================
+ Coverage   83.33%   83.35%   +0.01%     
==========================================
  Files         198      198              
  Lines       26791    26791              
==========================================
+ Hits        22327    22331       +4     
+ Misses       4464     4460       -4     

Impacted Files	Coverage Δ
panel/widgets/misc.py	95.08% <ø> (ø)
panel/widgets/select.py	94.89% <ø> (ø)
panel/widgets/player.py	80.00% <100.00%> (ø)
panel/io/server.py	78.30% <0.00%> (+0.21%)	⬆️
panel/io/state.py	69.58% <0.00%> (+0.24%)	⬆️
panel/io/reload.py	71.73% <0.00%> (+2.17%)	⬆️

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