Limit disk usage in Snapper configs

[geckolinux]

Discussed in #465

^{Originally posted by saberking December 5, 2022}
When installing Rolling I accidentally enabled snapshots for my home folder in addition to the system folders. The problem is that by default it is allowed to use 50% of the disk for system folder snapshots and 50% for home folder snapshots, allowing it to use in total 100% of my disk. This meant that I ran out of space completely and had a bit of a panic as I could not save anything. I have now disabled home folder snapshots and set the maximum space for system snapshots to 10%. This is probably nothing to do with Gecko but I thought I would share my experience anyway for any others who may run into this issue.