Add the Profile Sync Daemon Package & NixOS Module

Wasn't exactly sure what categories/subdirectories to put these under. It's a daemon that syncs your web browser profiles to tmpfs to increase speed/responsiveness & decrease ssd writes.
Is this not very long? If you make a change to your profile and reboot, the change won't be there, right? Does the daemon take a long time/much I/O to run? Maybe every 10m?