Allow multiple items to be added to a collection with one action

Similar to the "Set Variable" action, the "Add Item To Collection" action should allow multiple items to be added to a collection.

Currently, 1 item can be added to a collection at a time. If there are many items that need to be added, this creates a lot of actions. If they could be added in bulk, this would greatly reduce the visual footprint of our workflows, as well as the action count.