Add rich text field type to data models

Add a field type for rich text in data models like Contentful has. This can be very helpful for language translations when for example a word in a paragraph needs to be bolded in English but in another language the translation is two words or more and may be separated from each other - adding an input field for the bolded word(s) would not work in this case.

Related - https://ideas.builder.io/ideas/PROD-I-49