String list field type.
Renders as a dynamic list of text inputs with add / remove buttons.
Used for {:array, :string} attributes such as allowed origins, tags,
and so on. Sanitize strips HTML and trims each item; empty strings are
filtered out on parse_params/2.
See MishkaGervaz.Form.Behaviours.FieldType and MishkaGervaz.Form.Types.Field.