feat: add PriorityQueueDemo showing custom ordering using Comparator in PriorityQueue

Implemented PriorityQueueDemo.java to demonstrate reverse (max-heap) ordering
via a user-defined Comparator. Highlights how PriorityQueue can be customized
beyond natural ordering, using compare() logic to prioritize higher values.
Includes peek(), poll(), and iteration to show heap behavior before and after deletion.

Signed-off-by: https://github.com/Someshdiwan <someshdiwan369@gmail.com>

Author: Someshdiwan

Section 25 Collections Frameworks/Queue Interface/Priority Queue/src/PriorityQueueDemo.java

@@ -15,7 +15,6 @@ public static void main(String[] args) {
 
         PriorityQueue<Integer> PQ = new PriorityQueue<>(new MyComp());
 
-
         PQ.add(20);
         PQ.add(10);
         PQ.add(30);
@@ -33,4 +32,4 @@ public static void main(String[] args) {
 
         PQ.forEach((x)-> System.out.print(" "+x));
     }
-}
+}