feat: Add bidsignore implementation

[effigies]

Builds on #19. Will not try to integrate into the CLI until that's complete.

[codecov]

Codecov Report

Attention: Patch coverage is 84.29319% with 30 lines in your changes missing coverage. Please review.

Project coverage is 88.74%. Comparing base (a40bf21) to head (f47299b).

Files with missing lines	Patch %	Lines
src/bids_validator/bidsignore.py	69.49%	14 Missing and 4 partials ⚠️
src/bids_validator/types/files.py	84.28%	8 Missing and 3 partials ⚠️
tests/conftest.py	90.90%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
- Coverage   93.19%   88.74%   -4.46%     
==========================================
  Files           3        9       +6     
  Lines         191      382     +191     
  Branches       21       42      +21     
==========================================
+ Hits          178      339     +161     
- Misses          5       27      +22     
- Partials        8       16       +8     

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