Allow turbolift to toggle or set draft status for PRs

[rnorth]

Would help with usability of #11

[sledigabel]

Was partially addressed with this: #61
There doesn't seem to be an official way through the gh client to revert a "ready" PR to a draft.
cli/cli#2271

We would have to make use of the API, or use that approach:
https://github.com/kyanny/gh-pr-draft/blob/main/gh-pr-draft

[Dan7-7-7]

Is this still an issue after cli/cli#5995? Since we now presumably have turbolift foreach gh pr ready --undo
There might still be the problem of setting the default remote repository before this command will work. But I'm not sure whether that's an issue to be dealt with here.

[sledigabel]

Nice one, thanks for raising this @Dan7-7-7 ! Wasn't aware of cli/cli#5995, this is great news.

I'd be happy to close this PR, we could maybe discuss the possible shortcut of using turbolift update-prs with extra flags for this. I'll leave it open until our next turbolift review board.

cc @rnorth