Istanbul (or other code coverage tool) for custom end-to-end tests

We have a game GDK written in TypeScript, and we have a custom React/MobX/TypeScript framework to wrap the games and also for testing. We do unit tests through Jest, but we have our own custom end-to-end test framework for the games.

I'd like to be able to generate code coverage for these custom end-to-end tests. I'm wondering if Istanbul or another code coverage tool can help, or if we need to create our own tool from scratch.

Thanks!