[Enhancement] Save window size, position, and internal frame sizes on exit

[Rathain]

Simillar to issues #65 / #367, it would be great if the window size & position (and the position of the resizing adjustment between the columns and item image) were saved for future sessions.

The issue with the columns seems to be resolved, but the item image still gets cut off by default, requiring some fiddly manual resizing of the window after each launch. The problem has to do both with the default size of the overall window and the border between the columns and the image favoring the columns and cutting off the image.