Add dedicated widget for GPU Memory Usage

[thewan056]

I would like to see a separate dedicated widget for GPU Memory Usage. It would be the same layout as the RAM usage widget, with a different GPU Memory icon. Note that I use HWinfo.

Alternatively, create a generic widget that accepts any numerical input from hwinfo that we can put whatever value we like from hwinfo so that we can craft our own widgets showing whatever values we want. This is for more advanced users of course, so some breakage is expected. I would prefer this, as I want to monitor my usb UPS values from a widget too and being able to make multiple custom widgets using a generic template would be a huge plus for advanced users.