feat: --label GLOB filter

[ianlewis]

Description:

A new --label flag is added that takes a GLOB and matches against TODO labels. The flag can be included multilpe times. A TODO that matches any label is included in the output.

Related Issues:

Fixes #1562

Checklist:

• Review the CONTRIBUTING.md documentation.
• Add a reference to a related issue in the repository.
• Add a description of the changes proposed in the pull request.
• Add unit tests if applicable.
• Update documentation if applicable.
• Add a note in the CHANGELOG.md if applicable.
• Sign the Google CLA.

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 3 lines in your changes missing coverage. Please review.

Project coverage is 76.24%. Comparing base (865cd2b) to head (7e0273a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/cmd/todos/app.go	89.65%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1571      +/-   ##
==========================================
+ Coverage   75.94%   76.24%   +0.29%     
==========================================
  Files          17       17              
  Lines        1160     1187      +27     
==========================================
+ Hits          881      905      +24     
- Misses        203      205       +2     
- Partials       76       77       +1     

Files with missing lines	Coverage Δ
internal/walker/walker.go	60.07% <100.00%> (+1.48%)	⬆️
internal/cmd/todos/app.go	82.64% <89.65%> (-0.02%)	⬇️