All types are exported, but not all functions

[Egge21M]

index.ts exports all of model/types/index.js, but only selected functions are exported. This causes consumers to import functions that are not directly exported like this:

import { sumProofs } from "@cashu/cashu-ts/dist/lib/es5/utils";

We should make sure to only include exported members in the d.ts rollup. This can be done by either explicitly selecting exported types, or using typedoc tags and api-extractor's rollup feature

[gandlafbtc]

Let's fix this when move to modular exports.