I've built a custom FieldType, and I'd like editors to be able to add any fields using this FieldType to element indexes. Unfortunately, fields using my custom FieldType aren't included in the list of fields in the Customizable Element Index configurator.
How can I make it possible to add fields using my custom FieldType to element indexes?
Also, is it possible to define how the value returned from my custom FieldType displays in the element index?