The "itemSelector" configuration field type can be used by fragment developers to allow page authors to choose a content to be displayed by the fragment. Currently the field will allow authors to select any content of the selected types.
In some cases though, it is desirable to only allow the author to select specific content types, so that the fragment can expect to receive that exact type.
Beyond the type, it is desirable to select the sub-type and (if possible) the mime type.
This could be achieved through some additional typeOptions fields such as: itemType, itemSubtype and itemMimeType