Add command to create a worktree for a specified pull request

[wladpaiva]

Opened this issue mainly to discuss the possibility of creating a wt pr <NUMBER> command to handle worktree directly from a pull request number.

It's very handy because you don't always know by heart what branch is associated to a PR and in meetings we pretty much talk number and not necessary branch.

Other similar tool already offers this:
https://www.npmjs.com/package/@johnlindquist/worktree

[max-sixty]

great idea! added for GH. will try to add for GL too

I suspect there will be small issues so please lmk anything you find