matrix-lolopener.service: Use cli flags

Set the working directory to /opt/lolopener and use the -c cli flag to
set the config file path

matrix-lolopener.service

@@ -4,8 +4,8 @@ Description=LOL-Opener Matrix Bot
 [Service]
 Type=simple
 User=matrix-lolopener
-WorkingDirectory=/opt/matrix-lolopener/etc
-ExecStart=/opt/matrix-lolopener/bin/matrix-lolopener
+WorkingDirectory=/opt/matrix-lolopener
+ExecStart=/opt/matrix-lolopener/bin/matrix-lolopener -c etc/config.yml
 Restart=on-failure
 RestartSec=5