Add pop function to queue.md

queue.md

@@ -3,7 +3,7 @@
 <details>
 <summary>View contents</summary>
 <ol>
-    <li><a href="#pop-queue"><code>pop</code></a></li>
+    <li><a href="#pop"><code>pop</code></a></li>
     <li><a href="#back-queue"><code>back</code></a></li>
     <li><a href="#push"><code>push</code></a></li>
     <li><a href="#size-queue"><code>size</code></a></li>
@@ -16,6 +16,30 @@
 </ol>
 </details>
 
+# pop
+**Description** : pop() function is used to remove an element from the front of the queue (ie. the oldest element in the queue). The element is removed from the queue container and the size of the queue is decreased by 1.
+
+**Example**:
+```cpp
+    // Empty queue
+    queue<int> myqueue; 
+
+    // pushing elements into queue using push()
+    myqueue.push(0); 
+    myqueue.push(1); 
+    myqueue.push(2); 
+
+    // pop items from queue
+    myqueue.pop(); // pops 0 from queue
+    myqueue.pop(); // pops 1 from queue
+
+    // print contents of queue
+    while (!myqueue.empty()) { 
+        cout << ' ' << myqueue.front(); 
+        myqueue.pop(); 
+    } 
+```
+
 # push
 **Description** : push() function is used to insert an element at the back of the queue. The element is added to the queue container and the size of the queue is increased by 1.