Add search input for branches when adding a worktree

[Miqueas]

Details

As the title suggests, currently there's no option manually search for an existing branch when adding a worktree, which can be a little frustrating if the user has a lot of local branches. I've personally experienced this and that's why I'm opening this, so it would be useful to have the ability to search branches by typing the name.

Steps to reproduce

1. Click the "Add Worktree" icon button
2. Select the "Existing Branch" option

PR: #2394

[love-linger]

Merged

[Miqueas]

Thanks!