Interfaces do not build without a Module

[krisbitney]

Describe the bug An interface cannot build without a module. It can be desirable to define an interface so that multiple wrappers can share type definitions.

Expected behavior Users may expect an interface to build without a module so that types can be imported from it.

Additional context CIDT create an interface wrapper for the Near project and it does not build because there is no Module in the interface: https://github.com/polywrap/integrations/tree/near/borsh-wrapper/protocol/near/near-interface