fix type exports and polish `fedimint-ts`

[okjodom]

I pulled fedimint-ts v0.2.23 into my repo and got typing errors which I've now fixed. Now proposing we make a patch relese at v0.2.24. Alongside the type changes, I've just polished the lib to be more production like.

ERROR in ../../node_modules/fedimint-ts/FedimintClient.ts 1:12
Module parse failed: Unexpected token (1:12)
File was processed with these loaders:
 * ../../node_modules/source-map-loader/dist/cjs.js
You may need an additional loader to handle the result of these loaders.
> import type {
|   // BackupRequest,
|   InfoResponse,

ERROR in ../../node_modules/fedimint-ts/types.ts 1:0
Module parse failed: The keyword 'interface' is reserved (1:0)
File was processed with these loaders:
 * ../../node_modules/source-map-loader/dist/cjs.js
You may need an additional loader to handle the result of these loaders.
> interface Tiered<T> {
|   [amount: number]: T;
| }

webpack compiled with 2 errors and 11 warnings

[okjodom]

draft because this builds on top of #23 and #24

[okjodom]

cc @Kodylow