Handle disk space monitoring/notifications

### Problem

I think that's the only function we still rely on GSD Housekeeping for

### Proposal

Watch for disk usage and notify when the disk is almost full

### Prior Art (Optional)

GSD notifies:
* When the disk has 5% remaining
* When the disk has 1% remaining

But only when:
* The disk also has less than 1GB Remaining
* A warning hasn't been sent in the last 10 minutes

macOS:

Windows: