tests: Add lexer test for shebangs

tests: Add lexer test for symbols

tests: Add lexer test for keywords

tests: Add test for lexing booleans

tests: Test parser note mechanism

tests: Test text parsing with the lexer

tests: Comment test_parser_fuzz

parse: Decode file as UTF-8 ...

I was testing the parser with binary input.
Use Unicode instead and make sure we pass it that.

Add test harness and simple fuzz test