feat(zsh): teach `git hub link` to accept N parameters
feat(zsh): teach `git hub link` to accept N parameters

- 0: attempt to infer PR number from current branch.
- 1+: show links for all specified PR numbers.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent