add vertical space above and below room section

res/css/structures/_RoomSubList.scss

@@ -24,12 +24,14 @@ limitations under the License.
 .mx_RoomSubList_nonEmpty {
     min-height: 80px;
     flex: 1;
+    margin-bottom: 8px;
 }
 
 .mx_RoomSubList_labelContainer {
     display: flex;
     flex-direction: row;
     flex: 0 0 auto;
+    margin: 8px 19px 0 0;
 }
 
 .mx_RoomSubList_label {

src/components/structures/RoomSubList.js

@@ -348,7 +348,7 @@ const RoomSubList = React.createClass({
                     {this._getHeaderJsx()}
                 </div>;
             } else {
-                const heightEstimation = (len * 40) + 31;
+                const heightEstimation = (len * 40) + 31 + (8 + 8);
                 const style = {
                     flexGrow: `${heightEstimation}`,
                     maxHeight: `${heightEstimation}px`,