Hi Martin, welcome to LanguageTool! Great to hear about your plans to contribute. For the homophone topic, have you already checked out this wiki page and the list of confusion pairs (as we call them)?
Just recently, there was also a post about using neural networks to address this issue. Both approaches currently cannot deal with multi-token words like you're vs. your.
Please keep us updated and let us know if you have questions.
Regards
Daniel