Be able to remove subgroup from map

[jokd]

Is your feature request related to a problem? Please describe.
We are developing a function where the user can add layers from our geoserver catalogue and in case the layer is a Geoserver Layer Group it is split into the individual layers and put inside a subgroup of Mina lager. This subgroup should be able to be removed similar to how it works for individual layers.

Describe the solution you'd like
Context menu where the user can remove a subgroup