Add Jackal to XMPP Servers (#2545)

README.md

@@ -489,6 +489,7 @@ _[Extensible Messaging and Presence Protocol](https://en.wikipedia.org/wiki/XMPP
 #### XMPP Servers
 
 - [ejabberd](https://www.ejabberd.im/) - XMPP instant messaging server. ([Source Code](https://github.com/processone/ejabberd)) `GPL-2.0` `Erlang`
+- [jackal](https://github.com/ortuman/jackal) - XMPP server with focus on stability, simple configuration and low resource consumption. `Apache-2.0` `Go`
 - [Kontalk](http://kontalk.org/) - Kontalk is an Open Source Messenger, similar to WhatsApp (app for android only currently), including end-to-end encryption, server is based on Tigase XMPP Server. ([Source Code](https://github.com/kontalk)) `GPL-3.0` `Java`
 - [Metronome IM](https://metronome.im/) - Fork of Prosody IM. ([Source Code](https://github.com/maranda/metronome)) `MIT` `Lua`
 - [MongooseIM](https://www.erlang-solutions.com/products/mongooseim.html) - Mobile messaging platform with a focus on performance and scalability. ([Source Code](https://github.com/esl/MongooseIM)) `GPL-2.0` `Erlang`