Add syntax highlighting to template textareas

[a-kempka]

As Generico parses the template content, CSS and JavaScript directly the template-admins must be very careful when editing templates. E.g. inserting one blank line in the template body is not visible in the editor, but can lead to confusing results.

As of now the configuration of the templates takes place in plain <textarea>s which can be error prone.
I'd love to have syntax highlighting (and line numbering) applied to the , maybe with enlighterJS or any other engine.

As each of the textareas is mostly used for a specific engine, the textareas could even be configured with the appropriate language:

• HTML for the body of the template
• JavaScript for the custom JS
• CSS for the custom CSS
• PHP for dataset

The other input fields of a template could use a fixed width font (<pre>) as a default.
Even a fixed with font and a different background color of the text as opposed to the textarea could help to distinguish erroneous line breaks and spaces.