Add matterbridge to list of Matrix bridges (#974)

supporting-docs/projects/2017-08-21-matterbridge.md

@@ -0,0 +1,13 @@
+---
+layout: project
+title: matterbridge
+categories: projects other
+description: Bot for bridging Matrix and Mattermost, IRC, XMPP, Gitter, Slack, Discord, Telegram, Rocket.Chat, Hipchat(via xmpp), Steam.
+author: 42wim
+maturity: Stable
+---
+
+# {{ page.title }}
+This project implements bridges between Matrix rooms and Mattermost, IRC, XMPP, Gitter, Slack, Discord, Telegram, Rocket.Chat, Hipchat(via xmpp), Steam.
+
+Get it and report issues at [github](https://github.com/42wim/matterbridge)