add z-index to format bar so it appears above status area and reply wrapper

res/css/views/rooms/_MessageComposerFormatBar.scss

@@ -23,6 +23,9 @@ limitations under the License.
     border-radius: 4px;
     background-color: $message-action-bar-bg-color;
     user-select: none;
+    // equal to z-index of mx_ReplyPreview and mx_RoomView_statusArea (1000)
+    // but as it appears after them in the DOM, will appear on top.
+    z-index: 1000;
 
     &.mx_MessageComposerFormatBar_shown {
         display: block;