Add screensy to Communication - Custom Communication Systems (#2724)

Co-authored-by: Marijn <marijnvanwezel@gmail.com>

README.md

@@ -331,6 +331,7 @@ _See also: [Comparison of CalDAV and CardDAV implementations - Wikipedia](https:
 - [RetroShare](https://retroshare.cc) - Secured and decentralized communication system. Offers decentralized chat, forums, messaging, file transfer. ([Source Code](https://github.com/RetroShare/RetroShare)) `GPL-2.0` `C++`
 - [Revolt](https://revolt.chat/) - Revolt is a user-first chat platform built with modern web technologies. ([Source Code](https://github.com/revoltchat)) `AGPL-3.0` `Rust`
 - [Rocket.Chat](https://rocket.chat/) - Teamchat solution similar to Gitter.im or Slack. ([Source Code](https://github.com/RocketChat/Rocket.Chat)) `MIT` `Nodejs`
+- [Screensy](https://github.com/screensy/screensy) - Simple peer-to-peer screen sharing solution for sharing your screen with WebRTC. ([Demo](https://screensy.marijn.it)) `GPL-3.0` `Nodejs`
 - [Shhh](https://github.com/smallwat3r/shhh) - Keep secrets out of emails or chat logs, share them using secure links with passphrase and expiration dates. `MIT` `Python`
 - [Spectrum 2](https://spectrum.im/) - Spectrum 2 is an open source instant messaging transport.  It allows users to chat together even when they are using different IM networks. ([Source Code](https://github.com/SpectrumIM/spectrum2)) `GPL-3.0` `C++`
 - [Spreed](https://www.spreed.me/) - WebRTC audio/video calls, conferencing server, and web client. ([Source Code](https://github.com/strukturag/spreed-webrtc)) `AGPL-3.0` `Go`