(Scripts|SystemD)+mail fetch script and a SystemDservice/timer for it

Syncs every 3 hours.  Produces a notify-send message on fetching.

SystemD/.config/systemd/user/mail.service

@@ -0,0 +1,6 @@
+[Unit]
+Description=Syncing mail using mbsyncrc
+
+[Service]
+Type=simple
+ExecStart=%h/.local/scripts/mail_fetch

SystemD/.config/systemd/user/mail.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Run mail sync every 3 hours
+
+[Timer]
+OnBootSec=1min
+OnUnitActiveSec=10800
+Unit=mail.service
+
+[Install]
+WantedBy=timers.target