feat: add documentations via custom docs block

[tobiasdiez]

Fixes #49

[codecov]

Codecov Report

Merging #53 (0f11cda) into main (157dd57) will decrease coverage by 3.07%.
The diff coverage is 79.24%.

@@            Coverage Diff             @@
##             main      #53      +/-   ##
==========================================
- Coverage   96.47%   93.41%   -3.07%     
==========================================
  Files           3        3              
  Lines         284      319      +35     
  Branches       45       51       +6     
==========================================
+ Hits          274      298      +24     
- Misses         10       21      +11     

Impacted Files	Coverage Δ
src/core/indexer.ts	56.09% <50.00%> (-18.91%)	⬇️
src/core/parser.ts	97.63% <100.00%> (+0.13%)	⬆️
src/core/transform.ts	100.00% <100.00%> (ø)

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