Improvements for Param pane

[philippjfr]

• Add Tabulator as default DataFrame widget (if registered)
• Adds ability to use onkeyup configuration for TextInput widgets in Param pane

Fixes #3780

[codecov]

Codecov Report

Merging #3912 (b0dae21) into master (fa5c86d) will decrease coverage by 0.00%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##           master    #3912      +/-   ##
==========================================
- Coverage   83.30%   83.30%   -0.01%     
==========================================
  Files         222      222              
  Lines       32823    32835      +12     
==========================================
+ Hits        27344    27353       +9     
- Misses       5479     5482       +3     

Flag	Coverage Δ
ui-tests	35.20% <42.85%> (+0.01%)	⬆️
unitexamples-tests	75.04% <78.57%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
panel/param.py	87.22% <77.77%> (-0.18%)	⬇️
panel/widgets/input.py	95.68% <80.00%> (-0.18%)	⬇️

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