2 finger pan gesture support to select media

Although easy to implement for any app that uses a UITableView or a CollectionView, this feature is mainly in Apple's stock iOS apps. You select the items you want by swiping through them with your 2 fingers. This makes it easier for a user to select items rather than having to click the "select" button and then tap on the items item by item.

I've implemented this for the MediaCategoryView by adding two functions as per Apple's documentation: https://developer.apple.com/documentation/uikit/uitableviewdelegate/selecting_multiple_items_with_a_two-finger_pan_gesture

Instead of calling setEditing(), I call the delegate's setEditingStateChanged() function. In my testing it works pretty well.

Screen recording: