Intro to React

[hfaerber]

Existing lesson - https://frontend.turing.edu/lessons/module-3/react-1-the-what-and-the-why.html

• [x] Add lesson to SE curriculum repo
• [x] Expose link to lesson on lesson index page
• [ ] Update as needed

Notes:

• Add notes about useState
• Add key points from existing review session
• Consider mentioning that while JS can follow OOP, modern React follows a functional programming approach using hooks.