message: Add link to UMD demo to UMD dosc page
diff: @@ -11,6 +11,8 @@ To use the UMD build of `react-querybuilder`, link a `<script>` tag to the `/dis
  - `react-dnd-html5-backend@14`
  - `immer@6`
  +[Live demo](https://react-querybuilder.js.org/react-querybuilder/umd.html)
  +
  ## Example
  ```html
  