Add Ruby code blocks to the documents (#1200)

* Add Ruby code blocks to documents

* Remove Ruby code from en/docs

docs/chapter_tree/array_representation_of_tree.md

@@ -120,6 +120,12 @@
     val tree = mutableListOf( 1, 2, 3, 4, null, 6, 7, 8, 9, null, null, 12, null, null, 15 )
     ```
 
+=== "Ruby"
+
+    ```ruby title=""
+
+    ```
+
 === "Zig"
 
     ```zig title=""

docs/chapter_tree/avl_tree.md

@@ -211,6 +211,12 @@ 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=""
+
+    ```
+
 === "Zig"
 
     ```zig title=""

docs/chapter_tree/binary_tree.md

@@ -186,6 +186,12 @@
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title=""
+
+    ```
+
 === "Zig"
 
     ```zig title=""
@@ -423,6 +429,12 @@
     n2.right = n5
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_tree.rb"
+
+    ```
+
 === "Zig"
 
     ```zig title="binary_tree.zig"
@@ -579,6 +591,12 @@
     n1.left = n2
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_tree.rb"
+
+    ```
+
 === "Zig"
 
     ```zig title="binary_tree.zig"