Remotes tab

[Cretezy]

Continuation of #2

"Remotes" tab:

• List of remotes
• c to create
• r to rename
• d to delete
• e to edit? delete+create? Doesn't seem to currently exit in jj
• p to push highlighted remote
• f to fetch highlighted remote
• P to push all branches on highlighted remote
• F to fetch all remotes

Note: Will need to show error if not in a git repo. Ideally build in a way to support multiple backends.

Additionally, would be good to have an option to push after setting a branch.