Add docstring for split function and catch function, also try to make ExceptionGroup can work for now :)

[WindSoilder]

Hope this can help to solve #1

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@91a286f). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master       #3   +/-   ##
=========================================
  Coverage          ?   56.97%           
=========================================
  Files             ?       10           
  Lines             ?      251           
  Branches          ?       27           
=========================================
  Hits              ?      143           
  Misses            ?      103           
  Partials          ?        5

Impacted Files	Coverage Δ
exceptiongroup/_tools.py	56.06% <100%> (ø)
exceptiongroup/_tests/test_tools.py	100% <100%> (ø)
exceptiongroup/__init__.py	80.95% <100%> (ø)

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[njsmith]

Oh wow, thank you so much for picking this up! I have been feeling guilty about it for months :-).

A few comments, but really this is already an improvement; if you want to merge and then address them in a followup PR feel free.

[WindSoilder]

Very thanks for your encouragement and comments :) I have resolved them, please check and have a look.