This is a great project! Is there a place to look up the list of inbuilt lexers to understand the editor language support? Will forward to my (more hands-on devs) team members.
Lexing is handled by one of Mitchell's other projects, Scintillua. You'll find the source for all the built-in lexers in there. https://github.com/orbitalquark/scintillua
The documentation for Scintillua also gets pulled into Textadept's API documentation as a dependency, so the syntax is also explained there. It's basically a bridge between Scintilla's native lexing and LPeg.
The documentation for Scintillua also gets pulled into Textadept's API documentation as a dependency, so the syntax is also explained there. It's basically a bridge between Scintilla's native lexing and LPeg.