Add javascript questions guide

src/data/question-groups/javascript/content/reverse-string-function.md

@@ -0,0 +1,13 @@
+You can reverse a string using the `split()`, `reverse()`, and `join()` method.
+
+```javascript
+function reverseMyString(str) {
+  return str.split("").reverse().join("");
+}
+
+let myString = "Learn JavaScript";
+
+let reverseString = reverseMyString(myString);
+
+console.log(reverseString); // tpircSavaJ nraeL
+```