Export fields - "Handle type" column to analytics exports

Right now we return a contact's handle in an export, but not the type of handle. This makes it difficult for a user to identify how to fetch that contact by their handle from the API.

For example, if the handle was listed as "1234567890" - is this a custom handle / Intercom handle / something else?

Adding this would allow customers to quickly hit the {{GET /contacts/alt:[handle_type]:[handle]}} endpoint using resource aliases