Describe the feature or problem you’d like to solve

There is a REST api for canceling workflows, but https://cli.github.com/manual/gh_workflow doesn't support it.

Proposed solution

add gh run cancel $GITHUB_RUN_ID

How will it benefit CLI and its users?

Users won't have to write their own code to construct the URL and a curl request with credentials.

Additional context

I ended up implementing this myself, but I think a lot of what I'm doing would be nicer if I wasn't hand-rolling code.