Use navigation treeview aria pattern for roomlist sublists and tiles

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

res/css/views/rooms/_RoomTile.scss

@@ -143,6 +143,8 @@ limitations under the License.
 
 // toggle menuButton and badge on hover/menu displayed
 .mx_RoomTile_menuDisplayed,
+// or on keyboard focus of room tile
+.mx_RoomTile.focus-visible:focus-within,
 .mx_LeftPanel_container:not(.collapsed) .mx_RoomTile:hover {
     .mx_RoomTile_menuButton {
         display: block;