Improve Room Directory Look & Feel

By adding an icon next to the title.
Requires https://github.com/matrix-org/matrix-react-sdk/pull/848

src/skins/vector/css/vector-web/structures/_RoomDirectory.scss

@@ -28,6 +28,10 @@ limitations under the License.
     flex-direction: column;
 }
 
+.mx_RoomDirectory .mx_RoomHeader_simpleHeader {
+    margin-left: 0px;
+}
+
 .mx_RoomDirectory_list {
     flex: 1;