Description of JavaScript Promises in JavaScript Roadmap (#1646)

* Description of JavaScript Promises

* Updated the markdown file to the desired format

content/roadmaps/106-javascript/content/112-javascript-asynchronous-javascript/104-promises/readme.md

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 # Promises
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+Promises are a much better way to work with asynchronous code in JavaScript than the old and error-prone callback approach. They were introduced into JavaScript with ECMAScript 6. Using promises, we can manage extremely complex asynchronous code with rigorous error-handling set up, write code in a more or less synchronous style, and keep ourselves from running into the so-called callback hell.
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+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.codeguage.com/courses/advanced-js/promises-introduction'>A Detailed Introduction to Promises</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.codeguage.com/courses/advanced-js/promises-basics'>JavaScript Promises - Basics</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.codeguage.com/courses/advanced-js/promises-chaining'>JavaScript Promises - Chaining</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.codeguage.com/courses/advanced-js/promises-error-handling'>JavaScript Promises - Error Handling</BadgeLink>