Add command to view blamed commit's PR #102

Is your feature request related to a problem? Please describe.
I'd love it to be easier, given a line of code, to immediately open in my browser the blamed commit's PR. It would be especially useful now that I've started a new job, and I'm learning about the codebase.

Describe the solution you'd like
A command that, given a line of code in a repo, opens the blamed commit's PR in Github, probably with gh pr view

Describe alternatives you've considered
this seems straightforward technically