update readme

README.md

@@ -1,4 +1,15 @@
 Notifies using ntfy
 ===================
 
-I don't know what I'm doing yet
+Usage:
+
+```yaml
+      - name: Notify
+        uses: https://git.lerch.org/lobo/action-notify-ntfy@v1
+        if: always()
+        with:
+          host: ${{ secrets.NTFY_HOST }}
+          topic: ${{ secrets.NTFY_TOPIC }}
+          user: ${{ secrets.NTFY_USER }}
+          password: ${{ secrets.NTFY_PASSWORD }}
+```