Add .map and .reduce examples in preparation of React

**Description**
In Arrays section add example of `.map()` (used in React for generating lists) and `.reduce()` (idea used in useReducer).

**Where is the Content Located?**
https://geekwiseacademy.github.io/virtual-javascript/seven.html

**Old Content**
Text, Image, URL path, etc

**New Content**
Text, Image, URL path, etc
