Add support for NVMe disks when monitoring disk I/O
The system load monitor "Panel" applet 3.28.0 does not show disk I/O when NVMe disks are used (white box in the screen shot). This is because NVMe devices are named e.g. /dev/nvme0n1 instead of e.g. /dev/sda1.
This is a tracking bug. To be fixed via libgtop#43 (contains more details)