Add spreed (#782)

* Add Spreed WebRTC #645

* Fix

* Fix grammer

README.md

@@ -199,6 +199,7 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
   * [Node-Chat](https://github.com/IgorAntun/node-chat) - A not-so-basic open-source chat with admin features. `MIT` `Nodejs`
   * [RetroShare](http://retroshare.org) - Secured and decentralized communication system. Offers decentralized chat, forums, messaging, file transfer. ([Source Code](https://github.com/RetroShare/RetroShare)) `GPLv2` `С++`
   * [Rocket.Chat](https://rocket.chat/) - Teamchat solution similar to Gitter.im or Slack. ([Source Code](https://github.com/RocketChat/Rocket.Chat)) `MIT` `Nodejs`
+  * [Spreed](https://www.spreed.me/) - WebRTC audio/video calls, conferencing server, and web client. ([Source Code](https://github.com/strukturag/spreed-webrtc)) `AGPLv3` `Go`
   * [Synapse](https://matrix.org/blog/project/synapse/) - A server for [Matrix](https://matrix.org/), an open standard for decentralized persistent communication. ([Source Code](https://github.com/matrix-org/synapse)) `Apache` `Python`
     * [Matrix Console Web](https://matrix.org/blog/project/matrix-console-web/) - A web client meant to be a showcase of Matrix capabilities, and reference implementation of the Matrix standard. ([Source Code](https://github.com/matrix-org/matrix-angular-sdk)) `Apache` `Javascript`
     * [Vector](https://matrix.org/blog/project/vector/) - A glossy Matrix web client with an emphasis on performance and usability. ([Source Code](https://github.com/vector-im/vector-web)) `Apache` `Javascript`