[feat] Strict parsing

[Zffu]

Changelog:

• Seperated in-body AST parsing from outside-body parsing
• Added comparator lexer tokens instead of having to parse them from the AST side (now prevents operators from being written like '< ='
• Cleaned the codebase
• Cleaned all warnings
• Added comments on important parts of the codebase
• Fixed a bug with loop parsing for increment using parse_ast_value instead of parse_ast_value_in_body
• Fixed a bug with loop parsing where the ind was incremented by one after parsing the increment, causing a parsing error for the whole block.