Added additional tubesync workers

config/root/etc/s6-overlay/s6-rc.d/tubesync-db-worker/run

@@ -0,0 +1,5 @@
+#!/command/with-contenv bash
+
+exec nice -n "${TUBESYNC_NICE:-1}" s6-setuidgid app \
+    /usr/bin/python3 /app/manage.py process_tasks \
+    --queue database