Add content for react testing library

* Update 101-react-testing-library.md

updated Documentation

* Update content/roadmaps/100-frontend/content/115-testing-your-apps/101-react-testing-library.md

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/100-frontend/content/115-testing-your-apps/101-react-testing-library.md

@@ -1 +1,6 @@
-# React testing library
+# React Testing Library
+
+The React Testing Library is a very lightweight solution for testing React components. It provides light utility functions on top of react-dom and react-dom/test-utils, in a way that encourages better testing practices. Its primary guiding principle is: The more your tests resemble the way your software is used, the more confidence they can give you.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='blue' badgeText='Official Getting Started' href='https://testing-library.com/docs/react-testing-library/intro/'>