feature: Add drag and drop support

[lepa22]

Is your feature request related to a problem? Please describe. Sometimes I copy multiple items that I want to paste later to an application. Drag and drop functionality would be helpful to paste multiple copied items to an application.

Describe the solution you'd like I would like to be able to drag and drop copied items from Pano to an application. After dragging an item and dropping it to the desired application, Pano should remain open so I could then drag and drop another item.