Pls update HDD icons to SSD / NVME / HDD

[Strykar]

This is what just five disks (2x NVME, 2x SSD, 1x HDD) monitoring looks like on a 32 inch 2K resolution monitor.
The clock is in the middle of the screen for reference.

While adding text might be a solution for some like in #117
I quite like the approach of using our own icons as suggested in #83

An update to the disk icons so they appear different for NVME vs 2.5 inch SSD vs 3.5 inch HDD would be nice.
Maybe even just have an N / S / H in the icon would be enough?