Export vault interfaces (#1399)

## Description

Exports vault interfaces to fix
https://github.com/workos/workos-node/issues/1397

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[ ] Yes
```

If yes, link a related docs PR and add a docs maintainer as a reviewer.
Their approval is required.