I didn't review the code, just an early note: the Scintilla lexer should be first submitted to and accepted by the Scintilla project (https://www.scintilla.org/). Also the Ctags parser should be first submitted to and accepted by the Universal Ctags project (https://github.com/universal-ctags/ctags). See also https://github.com/universal-ctags/ctags/issues/1566#issuecomment-515902669 where someone also started a parser.
We want to stay inline with the upstream projects and so the code should be accepted there first.