Add Eloquent JavaScript book to front end roadmap (#1631)

Recommended because it's a very thorough and excellently written free, full-length textbook on JS. It's one of the resources that I most frequently saw mentioned when I was looking up how to learn JS, and it's the one that has helped me the most.

content/roadmaps/100-frontend/content/103-javascript/readme.md

@@ -11,6 +11,7 @@ JavaScript allows you to add interactivity to your pages. Common examples that y
 <ResourceGroupTitle>Free Content</ResourceGroupTitle>
 <BadgeLink badgeText='Read' colorScheme="yellow" href='https://www.w3schools.com/js/'>W3Schools – JavaScript Tutorial</BadgeLink>
 <BadgeLink badgeText='Read' colorScheme="yellow" href='https://javascript.info/'>The Modern JavaScript Tutorial</BadgeLink>
+<BadgeLink badgeText='Read' colorScheme="yellow" href='https://eloquentjavascript.net/'>Eloquent JavaScript textbook</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://youtu.be/hdI2bqOjy3c?t=2'>JavaScript Crash Course for Beginners</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://youtu.be/P7t13SGytRk?t=22'>Build a Netflix Landing Page Clone with HTML, CSS & JS</BadgeLink>
 <BadgeLink badgeText='Course' colorScheme='green' href='https://github.com/workshopper/javascripting'>Learn the basics of JavaScript</BadgeLink>