Provide a static binary with musl

[dufferzafar]

I couldn't use the binary provided as it builds with GLIBC and I'm on an older ubuntu, then I tried to build the package myself and got a linker error in tree-sitter due to some missing link time dependency so i finally tried cross to build me a static binary with musl. It was as easy as:

cargo install cross --git https://github.com/cross-rs/cross
cross build --release --target x86_64-unknown-linux-musl

ldd target/x86_64-unknown-linux-musl/release/gitu
      statically linked

Providing it along with current releases will be good for users with older systems.

[altsem]

months later... I spend some time to incorporate this :)
Will include it in the next release!

Here are some artifacts i managed to build from master if you'd like to verify:
Workflow run: https://github.com/altsem/gitu/actions/runs/20010026022/job/57378074499
Musl Download: https://github.com/altsem/gitu/actions/runs/20010026022/artifacts/4791395914