Add Wikipedia reference to BSGS algorithm Javadoc

Author: rajucreate

src/main/java/com/thealgorithms/maths/DiscreteLogarithmBSGS.java

@@ -13,7 +13,8 @@
  * <p>
  * Time complexity: O(√m)
  * Space complexity: O(√m)
- */
+ * @see <a href="https://en.wikipedia.org/wiki/Baby-step_giant-step">Baby-step giant-step algorithm</a>
+*/
 public class DiscreteLogarithmBSGS {
 
     /**