Export all types used as function params on index

[QuentinFrc]

Could be developer friendly to export type directly form index to able to do this import

import { Resend, CreateEmailOptions } from 'resend';

rather than this one

import { CreateEmailOptions } from 'resend/build/src/emails/interfaces';

My use case of needing thoses types is not really interesting but I think other peoples would make a great things with that

[ghosh]

This no longer works in 2.1.0, seems like the package build was changed in #259

[iBobik]

Just wanted to use the type, but cannot