Allow the use of an existing bridge interface?

[tgburrin]

I'm using UTM on an M1 and currently when I select bridged networking mode it creates a new bridge using the interface specified in the dialog. I'm wondering if it would be possible to allow people to select an existing bridge that they've already configured in the os. This might also allow people to use the bridge that mac creates by default, bridge0, where they can add additional interfaces.

Would this be possible to add as an option?