Only Sync when something has changed.

[Drallas]

I implemented Orbital Sync and it runs fine. 😅

Sync is happening at the INTERVAL_MINUTES I set, but it would be even better if it was only syncing on config / DNS changes.

Before I used docker-pihole-sync (A Docker Container To Sync Two Piholes) from @ShiromMakkad that did exactly that, only sync on change.

Sync on change and Rsync #186 would make Orbital Sync even better. (IMHO)