Handle disk space monitoring/notifications

[danirabbit]

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: