[TASK] Update fluid image viewhelper documentation

Adds PDF file example to the fluid "image" viewhelper documentation.
This demonstrates a capability of the image viewhelper that isn't currently
explained in the documentation.

Change-Id: Ice82c005ec66173c19d0f29efe069d23b3f46fdc
Resolves: #77348
Releases: master, 7.6
Reviewed-on: https://review.typo3.org/49292


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>

typo3/sysext/fluid/Classes/ViewHelpers/ImageViewHelper.php

@@ -46,7 +46,15 @@ use TYPO3\CMS\Core\Resource\FileReference;
  * (depending on your TYPO3s encryption key)
  * </output>
  *
- * <code title="non existing image">
+ * <code title="Other resource type (e.g. PDF)">
+ * <f:image src="fileadmin/user_upload/example.pdf" alt="foo" />
+ * </code>
+ * <output>
+ * If your graphics processing library is set up correctly then it will output a thumbnail of the first page of your PDF document.
+ * <img src="fileadmin/_processed_/1/2/csm_example_aabbcc112233.gif" width="200" height="284" alt="foo">
+ * </output>
+ *
+ * <code title="Non-existant image">
  * <f:image src="NonExistingImage.png" alt="foo" />
  * </code>
  * <output>