ntfy: add page (#14006)

Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/common/ntfy.md

@@ -0,0 +1,28 @@
+# ntfy
+
+> Send and receive HTTP POST notifications.
+> More information: <https://github.com/binwiederhier/ntfy>.
+
+- Send a message to the `security` topic:
+
+`ntfy pub security "{{Front door has been opened.}}"`
+
+- Send with a title, priority and tags:
+
+`ntfy publish --title="{{Someone bought your item}}" --priority={{high}} --tags={{duck}} {{ebay}} "{{Someone just bought your item: Platypus Sculpture}}"`
+
+- Send at 8:30am:
+
+`ntfy pub --at=8:30am {{delayed_topic}} "{{Time for school, sleepyhead...}}"`
+
+- Trigger a webhook:
+
+`ntfy trigger {{my_webhook}}`
+
+- Subscribe to a topic (Ctrl-C to stop listening):
+
+`ntfy sub {{home_automation}}`
+
+- Display help:
+
+`ntfy --help`