Update types for expect v1.20.2

[merrywhether]

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[dt-bot]

expect/index.d.ts

to author (@jmreidy). Could you review this PR?
👍 or 👎?

Checklist

• pass the Travis CI test?

[ghost]

Write your name on the same line. // Definitions by: Justin Reidy <https://github.com/jmreidy/>, Risto Keravuori <https://github.com/merrywhether/>

[ghost]

These look good. Longer-term, maybe this could use class Expectation<T> and declare function expect<T>(actual: T): expect.Expectation<T>; to help refine some of the methods there?

[merrywhether]

Thanks for the tip! Tried adding as much generics as made sense. Learning so much about TS doing this.