Add OpenRC service and basic documentation

services/openrc

@@ -0,0 +1,12 @@
+#!/sbin/openrc-run
+supervisor=supervise-daemon
+
+name="UniFi UPS safe shutdown"
+
+command="/usr/local/bin/unifi-shutd"
+command_args="<ip:port> <ups id> <scan interval> <bad scan limit>"
+
+depend() {
+        need net localmount
+        after firewall
+}