Install additional hicolor icon sizes.

[sebastic]

The additional icons are required for Debian Policy compliance, which requires at least 22x22 PNG icons:

Unless hidden by default, the desktop entry must point to a PNG or SVG icon with a transparent background, providing at least the 22×22 size, and preferably up to 64×64. The icon should be neutral enough to integrate well with the default icon themes. It is encouraged to ship the icon in the default hicolor icon theme directories, or to use an existing icon from the hicolor theme.

Debian Policy Manual 9.6 Menus

Only the 48x48 icon was already installed. Since there is no SVG icon for the scalable theme, the additional icons sizes are useful for all desktop environments that implement the desktop entry & icon theme specifications.

[Krakonos]

Thanks, I'm no sure why I didn't merge this earlier.