Update source and type input options

[flowscience]

This should be a Typeahead or a dropdown input that populates known types for the selected Source.

If the user wants to map a new type to the selected source, the type/schema selector should be rendered with available types: https://near.social/flowscience.near/widget/attestWithTypes for mapping new types to any given source; as well as an option to create a new type (using the type creator).

Select Source -> Render Known Types -> If new type, render type/schema selector -> If undefined type, render type creator