message: docs(zone.js): fix typos in NgZone guide code example
  Fixes
  PR Close
diff: @@ -29,8 +29,8 @@ To clarify how changes are detected and values updated, consider the following c
  ```javascript
  <html>
  <div id="dataDiv"></div>
  - <button id="btn">updateData<btn>
  - <canvas id="canvas"><canvas>
  + <button id="btn">updateData</button>
  + <canvas id="canvas"></canvas>
  <script>
  let value = 'initialValue';
  // initial rendering
  