make application window resizable to smaller width sizes

Musescore 4 does not have tabbing for displaying multiple scores in the same window. The user now has to have multiple windows open in order to copy/merge parts of various scores together. Currently on Macbook Pro 2012, with a screen resolution of 1280 by 800, MS 4 window size cannot be reduced enough to have two windows side-by-side. It can only be reduced to about 5/6 of the screen's width (see screenshot below). Even hiding the left panel doesn't allow a narrower width. Please consider allowing MS 4 window size to be reduced more (e.g., 640px) so that at least two scores can be displayed simultaneously on at least a standard mid laptop screen size ( e.g., 1280px) to allow easier going back and forth between two scores. (see initial post at https://musescore.org/en/node/335120#comment-1141775)

Narrowest width on Macbook 2012: with the left panel

Without the left panel