Support non-rust crates

[jyn514]

many non-rust projects release to github actions in a predictable manner; for example https://github.com/junegunn/fzf/ tags its releases and uploads binaries in a similar format to many rust projects. it would be really cool if binstall could install those programs without requiring them to be in the crates.io index. that would require a little more work from the user; binstall needs at least the URL of the github repo. but other than that i think this should be possible.

[NobodyXu]

It can be workaround by using --manifest-path to a crafted Cargo.toml containing the repository.

I agree we can improve that, my opinion is to allow user to specify url instead of crate name.