Upstream sync

README.md

@@ -119,3 +119,11 @@ To run the test suite create `.env.test.local` file containing the same entries
 ## CONTRIBUTING
 
 Make sure the test coverage remains at 100%, there are no rubocop complaints (`bundle exec rubocop`) and make a Pull Request.
+
+
+## Modifying parser and lexer
+
+* `rake lexer` - generates `lexer.rb` file based on `specification.rex` file
+* `rake parser` - generates `parser.rb` file based on `grammar.y` file
+* `rake generate` - generates both `lexer.rb` and `parser.rb` files
+