Typo3: Image description - accept html in fluid templates

For fluid templates:

was:
<f:format.nl2br>
Text with line breaks replaced by <br />

    <f:if condition="{file.properties.description}">
       <figcaption class="caption"><f:format.nl2br>{file.properties.description}</f:format.nl2br></figcaption>
   </f:if>

is:

<f:format.html>
Renders a string by passing it to a TYPO3 parseFunc. You can either specify a path to the TypoScript setting or set the parseFunc options directly. By default lib.parseFunc_RTE is used to parse the string.

The view helper must not be used in backend context, as it triggers frontend logic. Instead, use <f:sanitize.html /> to secure a given HTML string or <f:transform.html /> to parse links in HTML.

    <f:if condition="{file.properties.description}">
       <figcaption class="caption"><f:sanitize.html>{file.properties.description}</f:sanitize.html></figcaption>
   </f:if>