Add kotlin code block for chapter_heap (#1196)

* Add kotlin code block for chapter_hashing

* Add kotlin code block for chapter_heap.

docs/chapter_heap/heap.md

@@ -368,7 +368,38 @@
 === "Kotlin"
 
     ```kotlin title="heap.kt"
-
+    /* 初始化堆 */
+    // 初始化小顶堆
+    var minHeap = PriorityQueue<Int>()
+    // 初始化大顶堆（使用 lambda 表达式修改 Comparator 即可）
+    val maxHeap = PriorityQueue { a: Int, b: Int -> b - a }
+    
+    /* 元素入堆 */
+    maxHeap.offer(1)
+    maxHeap.offer(3)
+    maxHeap.offer(2)
+    maxHeap.offer(5)
+    maxHeap.offer(4)
+    
+    /* 获取堆顶元素 */
+    var peek = maxHeap.peek() // 5
+    
+    /* 堆顶元素出堆 */
+    // 出堆元素会形成一个从大到小的序列
+    peek = maxHeap.poll() // 5
+    peek = maxHeap.poll() // 4
+    peek = maxHeap.poll() // 3
+    peek = maxHeap.poll() // 2
+    peek = maxHeap.poll() // 1
+    
+    /* 获取堆大小 */
+    val size = maxHeap.size
+    
+    /* 判断堆是否为空 */
+    val isEmpty = maxHeap.isEmpty()
+    
+    /* 输入列表并建堆 */
+    minHeap = PriorityQueue(mutableListOf(1, 3, 2, 5, 4))
     ```
 
 === "Zig"