message: docs: display the beginning label in interpolation guide example
  Updating the doc to add the beginning label.
  I'm not sure if this was the way it was intended, but it looked strange with just an ending </label> tag.
  PR Close
diff: <div (keyup)="0">
  <h4>Template context: template reference variables (#customerInput):</h4>
  - <label>Type something:
  <!-- #docregion template-reference-variable -->
  - <input #customerInput>{{customerInput.value}}</label>
  + <label>Type something:
  + <input #customerInput>{{customerInput.value}}
  + </label>
  <!-- #enddocregion template-reference-variable -->
  </div>
  