Systemd service

1. Copy scripts/anilist-plex-sync.service to /etc/systemd/system/ and edit [Service] section.
2. Copy scripts/anilist-plex-sync.timer to /etc/systemd/system/ and edit the [Timer] section.
3. Execute these commands to enable the service and timer:

sudo systemctl daemon-reload
sudo systemctl enable anilist-plex-sync.service
sudo systemctl start anilist-plex-sync.service
sudo systemctl enable anilist-plex-sync.timer
sudo systemctl start anilist-plex-sync.timer

You can check if the timer is running with sudo systemctl list-timers and it should show something like this:
Mon 2021-05-31 13:38:02 CEST 3min 1s left n/a n/a anilist-plex-sync.timer anilist-plex-sync.service