Adds setWarning(<element>,...) and clearWarning() to mw.mmv.ui.Dialog.
These functions can be used to display a warning ribbon with the given
text in the reuse dialogs, typically when the copyright status of the
file is problematic (e.g. non-free or tagged with {{wrong licence}}).
Bug: T76030
Bug: T71389
Bug: T71557
Change-Id: I7c477c810d391578ec64635357eda97a85ab2954
Many users right-click on images as a way to download them.Due to this,
they may get a scaled-down version which is used for display purposes and
also not given guidance on how to attribute.
Bug: T75999
Change-Id: I30655a0dda4430b494a393f1fa708fce6ca6fafe
