SC2Mapster

First,

How does one contribute to this project?

In my playthrough, I've encountered tons of bugs and small issues, and I'd love to help fixing things.

Second, you might wish to include the answer to that question in the Description/Overview of the project. Also information about how to report bugs. I noticed the issues section only now. I had no clue how to report bugs and resorted to doing so in the comments.

You can try submitting patches in the issue thread as long as you only submit 1 patch/issue per thread.

I should warn you though that the developers do not seem too keen on fixing bugs, though. 7.2 is still very buggy and lots of bugs that have existed in 6.x are still around. It seems like they only really care about adding models. There was even a user who submitted a bunch of fixes with most of them being rejected. I would just start with submitting a few small ones before investing too much time here and see what the developers say/do about it.