This looks good, but, to my thinking, incomplete without support for Visual Prolog, which is what Lexilla'a lexer [actually targets][0]. I opened https://github.com/techee/geany/pull/4 to give an idea of what a more inclusive file def might look like.
[0]: https://github.com/ScintillaOrg/lexilla/blob/0bd13d84b3fef7a72553ab95c43d0d4...