Seconding this, docs are some of the best way to get involved. Alot of open source docs are very bare bones and maintainers are usually more than happy to get a docs PR.
I would absolutely agree with this, except OP says that they don't know the relevant language or framework well enough to write code - it's possible but unlikely that they'd have the ability to understand the code well enough to write proper documentation (though presumably they could read the documentation and fix grammatical mistakes and such).