Sensor reporting the list of mounted volumes / removable drives

[netmikey]

Is your feature request related to a problem? Please describe.
I have an external powered USB drive which I'd like to include in my automations. I have a smart plug controlling its power, but I'd need to know:

1. when the disk is mounted after it got powered on
2. when the disk unmounting is done before powering it off

Describe the solution you'd like
A sensor reporting the list of mounted volumes / removable drives (similar to the active microphone / webcam) would enable that functionality.

Additional context
n/a