feat: add support for action descriptions

[alexfertel]

Closes #29

[codecov]

Codecov Report

Merging #44 (b1268c7) into main (7354a71) will increase coverage by 0.8%.
Report is 3 commits behind head on main.
The diff coverage is 93.2%.

Additional details and impacted files

Files	Coverage Δ
src/check/mod.rs	84.7% <100.0%> (-0.6%)	⬇️
src/check/rules/structural_match.rs	90.2% <100.0%> (ø)
src/scaffold/emitter.rs	98.3% <100.0%> (+<0.1%)	⬆️
src/syntax/mod.rs	100.0% <ø> (ø)
src/syntax/tokenizer.rs	94.5% <100.0%> (+0.6%)	⬆️
src/syntax/ast.rs	93.3% <83.3%> (+1.0%)	⬆️
src/syntax/test_utils.rs	85.7% <85.7%> (ø)
src/hir/translator.rs	98.3% <92.5%> (+<0.1%)	⬆️
src/scaffold/modifiers.rs	90.8% <0.0%> (-4.8%)	⬇️
src/syntax/semantics.rs	87.9% <16.6%> (-5.3%)	⬇️
... and 1 more