Add regression testing resources (#1925)

* Update regression-testing.md

* Update content/roadmaps/113-qa/content/100-qa-basics/107-testing-techniques/100-functional-testing/regression-testing.md

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

content/roadmaps/113-qa/content/100-qa-basics/107-testing-techniques/100-functional-testing/regression-testing.md

@@ -1 +1,7 @@
-# Regression testing
+# Regression Testing
+
+Regression Testing is a type of software testing to confirm that a recent program or code change has not adversely affected existing features. Regression testing is a black box testing technique. Test cases are re-executed to check the previous functionality of the application is working fine and that the new changes have not produced any bugs.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.javatpoint.com/regression-testing'>Regression Testing</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.guru99.com/regression-testing.html'>What is Regression Testing with Test Cases</BadgeLink>