[FEATURE] Add a new field to the content object example

Resolves: #60421
Change-Id: I6287fab171503cc17fb1b0dc98ad444f23c740aa
Reviewed-on: http://review.typo3.org/32020
Reviewed-by: Tim Lochmüller <tim@fruit-lab.de>
Tested-by: Tim Lochmüller <tim@fruit-lab.de>