Add SUPPORT.md

https://help.github.com/articles/adding-support-resources-to-your-project/

.github/SUPPORT.md

+[**#matrix:matrix.org**](https://matrix.to/#/#matrix:matrix.org) is the official support room for Matrix, and can be accessed by any client from https://matrix.org/docs/projects/try-matrix-now.html 
+
+It can also be access via IRC bridge at irc://irc.freenode.net/matrix or on the web here: https://webchat.freenode.net/?channels=matrix