ZLS support

[tulilirockz]

Maybe this is out of scope, but also having a ZLS version fetcher would be pretty cool considering that it depends on the specific Zig versions (and most people will use zig + zls together)

[glyh]

zvm used to have this feature but it's broken for now. So, vote up for this issue.

[GalaxyShard]

I have been working on this in a fork (repo). It's working pretty well so far for stable and master releases of Zls. All it does is automatically clone Zls the first install, checkout to the proper commit (release tags, master, or user-selected if neither works), then compile it with the just-installed version of Zig.