This PR greatly improves the types within Puppeteer:
- **Almost everything** is auto-deduced.
- Parameters don't need to be specified in the function. They are deduced from the spread.
- Return types don't need to be specified. They are deduced from the function. (More on this below)
- Selections based on tag names correctly deduce element type, similar to TypeScript's mechanism for `getElementByTagName`.
- [**BREAKING CHANGE**] We've removed the ability to declare return types in type arguments for the following reasons:
1. Setting them will indubitably break auto-deduction.
2. You can just use `as ...` in TypeScript to coerce the correct type (given it makes sense).
- [**BREAKING CHANGE**] `waitFor` is officially gone.
To migrate to these changes, there are only four things you may need to change:
- If you set a return type using the `ReturnType` type parameter, remove it and use `as ...` and `HandleFor` (if necessary).
⛔ `evaluate<ReturnType>(a: number, b: number) => {...}, a, b)`
✅ `(await evaluate(a, b) => {...}, a, b)) as ReturnType`
⛔ `evaluateHandle<ReturnType>(a: number, b: number) => {...}, a, b)`
✅ `(await evaluateHandle(a, b) => {...}, a, b)) as HandleFor<ReturnType>`
- If you set any type parameters in the *parameters* of an evaluation function, remove them.
⛔ `evaluate(a: number, b: number) => {...}, a, b)`
✅ `evaluate(a, b) => {...}, a, b)`
- If you set any type parameters in the method's declaration, remove them.
⛔ `evaluate<(a: number, b: number) => void>((a, b) => {...}, a, b)`
✅ `evaluate(a, b) => {...}, a, b)`
