PLT-946 Add status icon to the left of the username in DM channel (#3258)

Add a StatusIcon component to be able to display a status icon from anywhere

webapp/sass/layout/_headers.scss

@@ -144,6 +144,8 @@
             white-space: normal;
         }
     }
+
+    @import "../components/status-icon";
 }
 
 .channel-intro {