Set GITHUB_TOKEN for cargo-binstall by default

[taiki-e]

#554 (comment)

The fact that cargo-binstall's performance or robustness would be worse without this env var at a high probability is very unfortunate.

cc @NobodyXu

Closes #561

[NobodyXu]

Thank you!

I've been reluctant to do this because of the implicit github-token passing.

I think we should put up documentation on this and someway to disable it?

[taiki-e]

the implicit github-token passing

Well, that's what the actions/checkout does, but it might indeed not be a good idea here.

[NobodyXu]

I will try to improve on cargo-binstall behavior, ideally users should not have to pass the github token, unless they are really installing a lot of crates or the crate itself doesn't provide any information in manifest and binstall has to figure out itself.

I think we can at least speed it up and avoid the need of token, for crate providing package.binstall with pkg-url