docs: Add DefaultTabController documentation

packages/mirai/lib/src/parsers/mirai_default_tab_controller/mirai_default_tab_controller.dart

@@ -8,8 +8,9 @@ part 'mirai_default_tab_controller.g.dart';
 @freezed
 class MiraiDefaultTabController with _$MiraiDefaultTabController {
   const factory MiraiDefaultTabController({
-    required Map<String, dynamic> child,
     required int length,
+    @Default(0) int initialIndex,
+    required Map<String, dynamic> child,
   }) = _MiraiDefaultTabController;
 
   factory MiraiDefaultTabController.fromJson(Map<String, dynamic> json) =>

packages/mirai/lib/src/parsers/mirai_default_tab_controller/mirai_default_tab_controller_parser.dart

@@ -19,6 +19,7 @@ class MiraiDefaultTabControllerParser
   Widget parse(BuildContext context, MiraiDefaultTabController model) {
     return DefaultTabController(
       length: model.length,
+      initialIndex: model.initialIndex,
       child: Mirai.fromJson(model.child, context) ?? const SizedBox(),
     );
   }

website/docs/widgets/default_tab_controller.md

@@ -0,0 +1,42 @@
+# DefaultTabController
+
+The Mirai DefaultTabController allows you to build a Flutter DefaultTabController widget using JSON.
+To know more about the DefaultTabController widget in Flutter, refer to the [official documentation](https://api.flutter.dev/flutter/material/DefaultTabController-class.html).
+
+## Properties
+
+| Property     | Type                    | Description                                                                 |
+|--------------|-------------------------|-----------------------------------------------------------------------------|
+| length       | `int`                   | The number of tabs.                                                         |
+| initialIndex | `int`                   | The initial index of the selected tab. Defaults to `0`.                     |
+| child        | `Map<String, dynamic>`  | The widget below this widget in the tree.                                   |
+
+## Example JSON
+
+```json
+{
+  "type": "defaultTabController",
+  "length": 3,
+  "child": {
+    "type": "column",
+    "children": [
+      {
+        "type": "tabBar",
+        "tabs": [
+          {"type": "tab", "text": "Tab 1"},
+          {"type": "tab", "text": "Tab 2"},
+          {"type": "tab", "text": "Tab 3"}
+        ]
+      },
+      {
+        "type": "tabBarView",
+        "children": [
+          {"type": "text", "data": "Content for Tab 1"},
+          {"type": "text", "data": "Content for Tab 2"},
+          {"type": "text", "data": "Content for Tab 3"}
+        ]
+      }
+    ]
+  }
+}
+```