Added SimpleX Chat to Custom Communication Systems (#2851)

README.md

@@ -333,6 +333,7 @@ _See also: [Comparison of CalDAV and CardDAV implementations - Wikipedia](https:
 - [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`
+- [SimpleX Chat](https://github.com/simplex-chat/simplex-chat) - The most private and secure chat and applications platform - now with double ratchet E2E encryption. `AGPL-3.0` `Haskell`
 - [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`
 - [StoneAge Messenger](https://cweb.gitlab.io/StoneAge.html) - A self-hosted Android messenger, S3-compatible storage is the only backend needed. ([Source Code](https://gitlab.com/cweb-repos/cweb-conversations), [Clients](https://f-droid.org/en/packages/com.cweb.messenger/)) `GPL-3.0` `Java`