I want to use this on 1.18.1. But there's no binaries for that version. So i need to compile from source. But i don't see any installation instruction on the main page or the wiki. How to do it?

It need to upgrade code first. You can't just compile it for version 1.18.1.

If you'd like to use for 1.18.1, you can compile my fork: https://github.com/solonovamax/JustMap, or for 1.18.2 you can use @umjammer's fork: https://github.com/umjammer/JustMap