message: fix(md-enhance): fix code demo toggle button
diff: border-color: transparent;
  border-radius: 50%;
  - background: #ccc;
  + background-color: #ccc;
  outline: none;
  font-size: 24px;
  cursor: pointer;
  #{hope-config.$dark-selector} & {
  - background: #555;
  + background-color: #555;
  }
  &:hover {
  - background: #aaa;
  + background-color: #aaa;
  #{hope-config.$dark-selector} & {
  - background: #777;
  + background-color: #777;
  }
  }
  }
  