Add support for Element / Matrix.org

[damienalexandre]

Element sells an ultra-secure messaging system — used by the French and German military already — which is built on a decentralised communications standard called Matrix (https://matrix.org/).

https://element.io/

Element is the fast, simple and private way to communicate with family, friends, teams, colleagues, organisations and the wider world. Old name is Riot.im. Works on Web, Android, iOS, macOS, Windows & Linux.

There seems to have some bots / apps available: https://element.io/element-matrix-store but no PHP SDK: https://matrix.org/sdks/

Matrix is an open standard and if we can manage to use it's API for what we do, we could theoretically support a large variety of new services like Element.

[damienalexandre]

Gitter is joining Matrix, in the long term it means the nice Gitter Client is a Matrix protocol compatible app!
https://matrix.org/blog/2020/09/30/welcoming-gitter-to-matrix