Add ntfy to Communication/Custom (#2927)

README.md

@@ -325,6 +325,7 @@ _See also: [Comparison of CalDAV and CardDAV implementations - Wikipedia](https:
 - [MiAOU](https://miaou.dystroy.org/login) - Multi-room persistent chat server. ([Source Code](https://github.com/Canop/miaou)) `MIT` `Nodejs`
 - [Mibew](https://mibew.org) - Mibew Messenger is an open-source live support application written in PHP and MySQL. It enables one-on-one chat assistance in real-time directly from your website. ([Demo](https://mibew.org/demo2), [Source Code](https://github.com/Mibew/mibew)) `Apache-2.0` `PHP`
 - [Mumble](https://wiki.mumble.info/wiki/Main_Page) - Low-latency, high quality voice/text chat software. ([Source Code](https://github.com/mumble-voip/mumble), [Clients](https://wiki.mumble.info/wiki/3rd_Party_Applications)) `BSD-3-Clause` `C++`
+- [ntfy](https://ntfy.sh/) - Push notifications to phone or desktop using HTTP PUT/POST, with Android app, CLI and web app, similar to Pushover and Gotify. ([Demo](https://ntfy.sh/app), [Source Code](https://github.com/binwiederhier/ntfy), [Clients](https://github.com/binwiederhier/ntfy-android)) `Apache-2.0/GPL-2.0` `Go`
 - [OTS](https://ots.fyi/) - One-Time-Secret sharing platform with a symmetric 256bit AES encryption in the browser. ([Source Code](https://github.com/Luzifer/ots)) `Apache-2.0` `Go`
 - [Papercups](https://papercups.io/) - An open source live customer chat web app written in Elixir. ([Demo](https://app.papercups.io/demo), [Source Code](https://github.com/papercups-io/papercups)) `MIT` `Elixir`
 - [PushBits](https://github.com/pushbits/server) - Self-hosted notification server for relaying push notifications via Matrix, similar to PushBullet and Gotify. `ISC` `Go`