[Feature Request] Create a build.md

[Spidy123222]

Currently it's hard to follow how to build muvm which increases the entry point to start building the project to contribute or test pull requests.

To build muvm it seems to need (asahi Linux) the library systemd-develinstalled. Libkrun.h file in krun-sys then have libkrunfw. It does seem krun-sys is its own rust build. Couldn't the dependencies be sub-modules to clone to then just build them all from the main directory with cargo build --release.

I honestly struggled building the project as there's no actions to try out pull requests or the main repo.