feat: Signing the tag

[panthony]

I don't know if this project is still active but it would be nice to be able to sign the tags created by ember release:

• https://git-scm.com/book/uz/v2/Git-Tools-Signing-Your-Work#Signing-Tags

I could provide a PR for this if you think it would be a nice to have.

[slindberg]

This is something I put off initially because I didn't know if anyone actually signed tags in the real world 😛 but it'd definitely would be great to support.

I could provide a PR for this if you think it would be a nice to have.

That would be awesome 👍

[mike-north]

Would love to see this. I'm starting to sign my releases across a bunch of addons