LibJS: Keep track of file names, lines and columns inside the AST

Author: https://github.com/boricj
Commit: 0039ecb189
Pull-request: https://github.com/SerenityOS/serenity/pull/5547
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibJS/Parser.h

@@ -222,6 +222,7 @@ private:
 
     Vector<Position> m_rule_starts;
     ParserState m_parser_state;
+    FlyString m_filename;
     Vector<ParserState> m_saved_state;
 };
 }