[TYPO3-mvc] translate placeholder for textarea

[Domi]

Hi Henjo

> <f:form.textarea ....
> additionalAttributes="{placeholder:'{f:translate(key:\'yourKey\')}'}" />
>
I did this in my code already, but the translation is not working. I 
only get the whole "{f:translate...}" in my output as placeholder.

Here my code again:
<f:form.textarea class="tinymce" cols="50" rows="20" property="message" 
additionalAttributes="{required:'required', 
placeholder:'{f:translate(key=\'tx_intranet_domain_model_messages.message\')}'}"/> 


Cheers,
Dominic