Make files in the editor drag-able out of the window to other programs

[nm17]

Is your feature request related to a problem? Please describe.
It would be great if I could drag-and-drop files out of the viewer to other programs like GIMP.

Describe the solution you'd like
Make files drag-able out of the editor.

Describe alternatives you've considered
Right now, you can open files using the Open or Edit button, but dragging out files out of the texture pack editor could be useful too.

Additional context
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