Automatically detect and use linked worktrees registered with a local content source

A linked worktree allows a user to keep multiple branches checked out at once. (In other words, have one worktree per branch). These can be very useful for editing content across branches. Currently, Antora only recognizes and picks up the main worktree (the directory that contains the .git folder).

If a local content source (i.e., local git clone) has linked worktrees, autodetect them and use the worktree (local folder) for the ones where the HEAD matches a content branch.

A user should be able to add and remove worktrees attached to a local content source (git clone) and Antora should automatically detect and make use of those worktrees in the event the current branch of the worktree matches a content branch. No changes should be required to the author's playbook.