[typescript] Export all types of the public API

### What problem does this feature solve?
Typescript has the oddity that you can export a type, but not the types it depends on, e.g. members or member function parameters.

I see a couple of tickets in the repo that try to address this by requesting "export type X".

But simply all types of the public API should be accessible. Else the user always has to play tricks like this:

```
export type OptionDataItemObject = Extract;
```

to get what we need. This should not be necessary.

### What does the proposed API look like?
All publicly declared types are exported.