Implement file globbing support

[simaoafonso-pwt]

This is tested locally in tcsh and bash, zsh is untested.

There should not be any regressions, the test suite passes. We can bikeshed the name.

I did not add support for globbing folders, this doesn't seem to be supported in zsh. I also did not implement the sub-folder support (that is, showing all folders on the file glob completion, so you can descend the hierarchy) since this is only supported in bash. I accept this feature might be required, and are willing to implement it.

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This is based on https://github.com/iterative/shtab/blob/main/examples/customcomplete.py#L11-L22.

For zsh, https://zsh-manual.netlify.app/completion-system mentions there's no support for globbing folders.

Fix #124 #69

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 9 lines in your changes missing coverage. Please review.

Project coverage is 88.20%. Comparing base (1d7a36b) to head (201dcc2).

Files with missing lines	Patch %	Lines
shtab/__init__.py	66.66%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #186      +/-   ##
==========================================
- Coverage   88.88%   88.20%   -0.69%     
==========================================
  Files           3        3              
  Lines         360      373      +13     
==========================================
+ Hits          320      329       +9     
- Misses         40       44       +4     

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