introduce mod/notification-ntfy...

... for sending notifications via Ntfy (https://ntfy.sh/).

TODO: use proper formatting once supported in Android app:
https://github.com/binwiederhier/ntfy/issues/889

doc/mod/notification-ntfy.md

@@ -0,0 +1,79 @@
+Send notifications via Ntfy
+===========================
+
+[⬅️ Go back to main README](../../README.md)
+
+> ℹ️️ **Info**: This module can not be used on its own but requires the base
+> installation. See [main README](../../README.md) for details.
+
+Description
+-----------
+
+This module adds support for sending notifications via
+[Ntfy](https://ntfy.sh/). A queue is used to make sure
+notifications are not lost on failure but sent later.
+
+Requirements and installation
+-----------------------------
+
+Just install the module:
+
+    $ScriptInstallUpdate mod/notification-ntfy;
+
+Also install the Ntfy app on your mobile device or use the
+[web app](https://ntfy.sh/app) in a browser of your choice.
+
+Configuration
+-------------
+
+Creating an account is not required. Just choose a topic and you are good
+to go.
+
+> ⚠️ **Warning**: If you use ntfy without sign-up, the topic is essentially
+> a password, so pick something that's not easily guessable.
+
+Edit `global-config-overlay`, add `NtfyServer` (leave it unchanged, unless
+you are self-hosting the service) and `NtfyTopic` with your choosen topic.
+Then reload the configuration.
+
+> ℹ️ **Info**: Copy relevant configuration from
+> [`global-config`](../../global-config.rsc) (the one without `-overlay`) to
+> your local `global-config-overlay` and modify it to your specific needs.
+
+Usage and invocation
+--------------------
+
+There's nothing special to do. Every script or function sending a notification
+will now send it to your Ntfy topic.
+
+But of course you can use the function to send notifications directly. Give
+it a try:
+
+    $SendNtfy "Subject..." "Body..."
+
+Alternatively this sends a notification with all available and configured
+methods:
+
+    $SendNotification "Subject..." "Body..."
+
+To use the functions in your own scripts you have to declare them first.
+Place this before you call them:
+
+    :global SendNtfy;
+    :global SendNotification;
+
+In case there is a situation when the queue needs to be purged there is a
+function available:
+
+    $PurgeNtfyQueue;
+
+See also
+--------
+
+* [Send notifications via e-mail](notification-email.md)
+* [Send notifications via Matrix](notification-matrix.md)
+* [Send notifications via Telegram](notification-telegram.md)
+
+---
+[⬅️ Go back to main README](../../README.md)  
+[⬆️ Go back to top](#top)