Handle toHaveBeenCalled

[Qziem]

Good to write bindings for toHaveBeenCalled, toHaveBeenCalledWith,... and other methods for mock functions.

[DZakh]

You can reimplement toHaveBeenCalled with something like this:

let mockFoo = Jest.JestJs.fn(() => ())

expect(mockFoo->Jest.MockJs.calls->Js.Array2.length)->JExp.not_->JExp.toBe(0, _)

But, yeah, it would be great to have more bindings out of the box :)