added ufw firewall application preset (fixes #2435)

etc/firewall-ufw/README.md

@@ -0,0 +1,21 @@
+Uncomplicated FireWall application preset
+===================
+Installation
+-----------
+**Please note:** When you installed syncthing using the official deb package, you can skip the copying.
+
+Copy the file `syncthing` to your ufw applications directory usually located at `/etc/ufw/applications.d/`. (root permissions required).
+
+Then run
+```
+sudo ufw app update syncthing
+```
+to load the preset.
+To allow the syncthing ports, run:
+```
+sudo ufw allow syncthing
+```
+You can also verify the opened ports:
+```
+sudo ufw status verbose
+```

etc/firewall-ufw/syncthing

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+[syncthing]
+title=Syncthing
+description=Syncthing file synchronisation
+ports=22000/tcp|21027/udp