Add TypeScript types for api

**Feature request**
It would be great to have import for helpers.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_import` with default `false`.

The issue names no files, tests, or entry points, and its title conflicts with the request for helper imports and the enable_import configuration option. Start by locating the API configuration parser and existing helper-import or type-definition tests. Confirm the intended scope with maintainers; done should include a documented behavior and coverage for the default false setting.

Written by the indexing model from the issue text.