[Feature Request] Show git status on the right side of each worktree

Rough sketch of the new UI is:

```
main
worktree-1 +200 -100 1 commit ahead / 2 commits behind
worktree-2 +10 -200
worktree 1 commit ahead
```

The number indicates ongoing, unstaged changes, and ahead and behind are compared with the local main worktree.

Please let me know what you think about this feature, and feel free to assign this to me.