Consider adding a small swapfile to rootfs to avoid excessive zram pagefile negotiations

As described in this forum thread, a small swapfile in rootfs has been observed to aid system responsiveness and stability by alleviating excessive pagefile negotiations in zram. My personal anecdote it that even a swapfile of 512MiB was shown to be helpful but, of course, a larger swapfile is beneficial as disk space requirements allow.

This ticket serves as an argument in favor of the default L5 PureOS configuration mitigating performance/stability issues derived from the relatively limited disk space in the 32GB L5.