that's exactly why it would be great if we could get some help/guidance from Geany/Scintilla contributors to make it happen.
Both projects' respective mailing lists have a fair few helpful and knowledgeable people:
https://geany.org/support/mailing-lists/ https://groups.google.com/g/scintilla-interest?pli=1
Geany also has an IRC channel (#geany on FreeNode) that often has one or two developers in it, depending on the timezone.
Also it's probably useful to look at various other such endeavors to see where to edit Geany's code:
https://github.com/geany/geany/commit/07002d252a36b77d150536ffe0c860fa91f4f6... https://github.com/geany/geany/commit/94aa892c8177e93d0dff3edf853854e872f19d... https://github.com/geany/geany/commit/b1f93c29770a9de30c2172ce7ee6ad5ca981c9...
For Scintilla, there's also a useful tutorial (using a language as obscure as Julia 😉) that explains how to implement a lexer. It used to be linked from Scintilla's main documentation page but it 404's here. I found it hosted elsewhere:
https://www.coursehero.com/file/45607974/Scintilla-varaq-Tutorialpdf/
github-comments@lists.geany.org