add firewalld config file

Author: feschber

README.md

@@ -97,6 +97,10 @@ gtk-update-icon-cache /usr/local/share/icons/hicolor/
 # install desktop entry
 sudo mkdir -p /usr/local/share/applications
 sudo cp de.feschber.LanMouse.dekstop /usr/local/share/applications
+
+# when using firewalld: install firewall rule
+sudo cp firewall/lan-mouse.xml /etc/firewalld/services
+# -> enable the service in firewalld settings
 ```
 
 ### Conditional Compilation

firewall/lan-mouse.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- for packaging: /usr/lib/firewalld/services/lan-mouse.xml -->
+<!-- configure manually: /etc/firewalld/services/lan-mouse.xml -->
+<service>
+  <short>LAN Mouse</short>
+  <description>mouse and keyboard sharing via LAN</description>
+  <port port="4242" protocol="udp"/>
+</service>