Add field formatter for text fields

Currently the field formatter only supports entity reference fields, namely for media references.

It would be nice to gradually extend this to any (multi-value) field type.

We currently have a customer asking for "swipeable content cards". The idea is to make values in a multi-value formatted text field horizontally scrollable (swipeable).

Let's provide a SwiffySliderTextFormatter (allowing the text formatter via settings).