Add Matrix button

README.md

@@ -1,6 +1,8 @@
 Mwmbl: No ads, no tracking, no cruft, no profit
 ===============================================
 
+[![Matrix](https://img.shields.io/matrix/mwmbl:matrix.org?color=blue&label=Matrix)](https://matrix.to/#/#mwmbl:matrix.org)
+
 Mwmbl is a non-profit, ad-free, free-libre and free-lunch search
 engine with a focus on useability and speed. At the moment it is
 little more than an idea together with a [proof of concept