Add atap function

[Constantiner]

Add async version of tap function to handle side effects.

It is like identity function but has a function as argument.

const log = data => console.log(data);

const someData = "123";
const someDataPromise = Promise.resolve(someData);
atap(log)(someDataPromise).then(resultingData => expect(resultingData).toBeEqual(someData));

It prints 123 in console.