Give the show more button some real CSS

This is still somewhat placeholder.

res/css/views/rooms/_RoomSublist2.scss

@@ -38,5 +38,14 @@ limitations under the License.
         display: flex;
         flex-direction: column;
         overflow: hidden;
+
+        .mx_RoomSublist2_showMoreButton {
+            height: 44px; // 1 room tile high
+            cursor: pointer;
+
+            // We create a flexbox to cheat at alignment
+            display: flex;
+            align-items: center;
+        }
     }
 }

src/components/views/rooms/RoomSublist2.tsx

@@ -237,11 +237,10 @@ export default class RoomSublist2 extends React.Component<IProps, IState> {
 
                 // TODO: CSS TBD
                 // TODO: Make this an actual tile
-                const moreTileHeightPx = layout.tileHeight;
                 visibleTiles.splice(visibleTiles.length - 1, 1, (
                     <div
                         onClick={this.onShowAllClick}
-                        style={{height: moreTileHeightPx, lineHeight: moreTileHeightPx, cursor: 'pointer'}}
+                        className='mx_RoomSublist2_showMoreButton'
                         key='showall'
                     >
                         {_t("Show %(n)s more", {n: numMissing})}