Import of other definitions

Currently we rely on `/// ` to import another definitions to ours.

That's fine for testing, but I don't think that will work after publishing to DefinitelyTyped. So we should research this problem and maybe solve it in a more conventional way.

Start by examining the `/// ` usage and the definitions it imports. Research how DefinitelyTyped packages conventionally import other definitions, then verify that the chosen approach still resolves correctly after publishing; done means the definitions no longer depend on the testing-only relative reference.

Written by the indexing model from the issue text.