Help us improve 🍉's TypeScript support

0.25 came with a huge improvement in the quality and maintainability of 🍉's TypeScript types. There were some teething problems, requiring a few patch releases, and no doubt the increased type coverage revealed new TS errors that weren't there before.

Anyway, thanks a lot to @sidferreira @paulrostorp @enahum @mlecoq for their contributions

You can help. Here's a few TS maintenance items that need to be done:

• hook up prettier to run over .d.ts
• in package.json there are outdated TS-related dependencies… I'm not even sure that all of them should be there, given that much of the TS checking lives in examples/typescript
• remove // @flow comments from d.ts's
• there's tslint, but I don't think it's hooked up to run anywhere? shouldn't it be a part of yarn ci:check ?
• add usage of more 🍉 APIs to examples/typescript to test type-checking
• add typescript types to documentation