Allow format any text field (string and string_long)

I added a new field formatter, but I think that the old one it's compatible too. I copied the old formatter code, change the field_types and cast values in lines 191 and 192.

@psf_ thanks for the contribution!

I've looked at the merge request, and I'm wondering why we extend the field_types</codes> of the <code>ssch_formatter with your suggestions. And if I'm not mistaken, when these field types are used, there is no language value available, and the highlighting uses the automatic language detection mechanism, but when we do this, we have to point the user to https://github.com/scrivo/highlight.php?tab=readme-ov-file#automatic-lan....

Now that I have read the automatic language detection mode instructions of the scrivo/highlight.php again, I think it might be better not to provide the user with the option to use "regular text fields" and the one provided in this module. Maybe extending the module's README.md with a note on this automatic language detection mode (and also in the service itself) is better.