Add ReverseStringUsingStack utility for reversing strings using stack

Author: navaneedan07

src/main/java/com/thealgorithms/stacks/ReverseStringUsingStack.java

@@ -13,12 +13,15 @@ private ReverseStringUsingStack() {
     public static String reverse(String str) {
         Stack<Character> stack = new Stack<>();
         StringBuilder reversedString = new StringBuilder();
-
-        if (str.isEmpty())
+        // Check if the input string is empty
+        if (str.isEmpty()) {
             return str;
+        }
+        // Push each character of the string onto the stack
         for (char i : str.toCharArray()) {
             stack.push(i);
         }
+        // Pop each character from the stack and append to the StringBuilder
         while (!stack.isEmpty()) {
             reversedString.append(stack.pop());
         }