message: Update README with demo
diff: @@ -28,7 +28,12 @@ You'll then need to add the `suspenseExchange`, that this package exposes, to yo
  `urql` Client and set the `suspense` mode to `true`:
  ```js
  -import { createClient } from 'urql';
  +import {
  + createClient,
  + dedupExchange,
  + cacheExchange,
  + fetchExchange,
  +} from 'urql';
  import { suspenseExchange } from '@urql/exchange-suspense';
  const client = createClient({
  @@ -80,3 +85,5 @@ const YourContent = () => {
  <YourContent />
  </SuspenseBoundary>;
  ```
  +
  +[You can also find a fully working demo on CodeSandbox.](https://codesandbox.io/s/urql-client-side-suspense-demo-81obe)
  