feat: add ruby code blocks - chapter tree (#1293)

docs/chapter_tree/array_representation_of_tree.md

@@ -123,7 +123,9 @@
 === "Ruby"
 
     ```ruby title=""
-
+    ### 二叉树的数组表示 ###
+    # 使用 nil 来表示空位
+    tree = [1, 2, 3, 4, nil, 6, 7, 8, 9, nil, nil, 12, nil, nil, 15]
     ```
 
 === "Zig"

docs/chapter_tree/avl_tree.md

@@ -214,7 +214,18 @@ AVL 树既是二叉搜索树，也是平衡二叉树，同时满足这两类二
 === "Ruby"
 
     ```ruby title=""
+    ### AVL 树节点类 ###
+    class TreeNode
+      attr_accessor :val    # 节点值
+      attr_accessor :height # 节点高度
+      attr_accessor :left   # 左子节点引用
+      attr_accessor :right  # 右子节点引用
 
+      def initialize(val)
+        @val = val
+        @height = 0
+      end
+    end
     ```
 
 === "Zig"

docs/chapter_tree/binary_tree.md

@@ -189,7 +189,16 @@
 === "Ruby"
 
     ```ruby title=""
+    ### 二叉树节点类 ###
+    class TreeNode
+      attr_accessor :val    # 节点值
+      attr_accessor :left   # 左子节点引用
+      attr_accessor :right  # 右子节点引用
 
+      def initialize(val)
+        @val = val
+      end
+    end
     ```
 
 === "Zig"
@@ -432,7 +441,18 @@
 === "Ruby"
 
     ```ruby title="binary_tree.rb"
-
+    # 初始化二叉树
+    # 初始化节点
+    n1 = TreeNode.new(1)
+    n2 = TreeNode.new(2)
+    n3 = TreeNode.new(3)
+    n4 = TreeNode.new(4)
+    n5 = TreeNode.new(5)
+    # 构建节点之间的引用（指针）
+    n1.left = n2
+    n1.right = n3
+    n2.left = n4
+    n2.right = n5
     ```
 
 === "Zig"
@@ -594,7 +614,13 @@
 === "Ruby"
 
     ```ruby title="binary_tree.rb"
-
+    # 插入与删除节点
+    _p = TreeNode.new(0)
+    # 在 n1 -> n2 中间插入节点 _p
+    n1.left = _p
+    _p.left = n2
+    # 删除节点
+    n1.left = n2
     ```
 
 === "Zig"