Nullish Coalescing

# Nullish Coalescing This is a new operator `??` which is meant to augment the common usage of `||` in the same way `===` augments `==` as a more strict form of equality. To understand it, let's look a how || works: 

const response = {
  nullValue: null,
  headerText: "",
  animationDuration: 0,
  height: 400,
  showSplashScreen: false,
} as const;

const undefinedValue = response.undefinedValue || "some other default";
// This would be: 'some other default'

const nullValue = response.nullValue || "some other default";
// These two examples work similar in most languages. As a tool || is pretty good at defaulting things, but JavaScript's falsy checks can surprise you for some common values: Potentially unintended. '' is falsy, result: 'Hello, world!' 
const headerText = response.headerText || "Hello, world!";

// Potentially unintended. 0 is falsy, result: 300
const animationDuration = response.animationDuration || 300;

// Potentially unintended. false is falsy, result: true
const showSplashScreen = response.showSplashScreen || true;
// When switching to use ?? instead, then === equality is used to compare the two sides: 
const emptyHeaderText = response.headerText ?? "Hello, world!";
const zeroAnimationDuration = response.animationDuration ?? 300;
const skipSplashScreen = response.showSplashScreen ?? true;