Feauture request unmount resized image.

[elovejoy-nyle]

Fist off, this project is so boss, I love it!
I did notice the loop back device was still mounted, and listing the original file-size after the resize operation completed.
all i did was unmount and remount the disk image, and there was no issue. but I thought it might be a bit confusing, in the case where someone uses a utility like gnome-disks to inspect the image file change, rather than looking at the size of the image on disk.

Just a thought.