🏷️(helix) add types for @helpscout/helix package

[jbpenrath]

Purpose

We are using @helpscout/helix to create factories for our frontend tests. Currently this package has no type so we have no guarantee that our factories stick to real objects implementation. As a little challenge to level up in typescript and in order to improve our factories frontend, I decided to try to type this package.

If this type is reliant from our side, I'm thinking about submit a PR to add these types within definitelyTypes.

Proposal

• [x] Type @helpscout/helix package