feat: add --skip-modifiers flag

[alexfertel]

Resolves #66

Note that I named the flag --skip-modifiers (or -m) because that's slightly more accurate and is consistent with the other flags.

[codecov]

Codecov Report

Attention: Patch coverage is 92.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.9%. Comparing base (3991e37) to head (1d83b51).

❗ Current head 1d83b51 differs from pull request most recent head d90a863

Please upload reports for the commit d90a863 to get more accurate results.

Additional details and impacted files

Files	Coverage Δ
src/check/context.rs	88.3% <100.0%> (+0.1%)	⬆️
src/check/rules/structural_match.rs	96.1% <100.0%> (+<0.1%)	⬆️
src/hir/combiner.rs	95.6% <ø> (-0.1%)	⬇️
src/hir/mod.rs	100.0% <100.0%> (ø)
src/sol/translator.rs	98.8% <100.0%> (+<0.1%)	⬆️
src/check/mod.rs	91.2% <75.0%> (-0.9%)	⬇️
src/config.rs	86.1% <85.7%> (-0.6%)	⬇️
src/scaffold/mod.rs	87.5% <50.0%> (-0.9%)	⬇️

... and 2 files with indirect coverage changes