feat: support scp-style SSH urls for Git source

[orhun]

We now support:

source:
  git: [email protected]:killercup/cargo-edit.git

Todo list:

• Update documentation about this new key
• Update one of the examples to use this

closes #672

[baszalmstra]

Nice! We also need to add this to the https://github.com/prefix-dev/recipe-format

[wolfv]

I think we don't need to update examples or even docs. But it would be good to use this in one of the end-to-end tests or another test. And the lint needs fixing. Then I am happy to merge!

[orhun]

Looks like there is a problem with using SSH URLs in the CI:

[email protected]: Permission denied (publickey).
fatal: Could not read from remote repository.

[orhun]

We need to add an SSH key to clone over SSH 💀

https://stackoverflow.com/questions/60222741/github-actions-and-git-clone-issue

[wolfv]

Hmm, well, if there is no quick way of testing that it might not matter that much. We could add a test that just makes sure that we can parse these.