fix: 修复assets在example app中不能使用的问题 & 加入maven local的链接，修复flutter无法打包 aar的问题

lib/widgets/chat_footer.dart

@@ -49,7 +49,7 @@ class _ChatFooterState extends State<ChatFooter>
             child: GestureDetector(
               onTap: widget.onClear,
               child: Image.asset(
-                'assets/images/delete.png',
+                'assets/images/delete.png',package: 'ai_chat_assistant',
                 width: 24,
                 height: 24,
               ),
@@ -137,7 +137,7 @@ class _ChatFooterState extends State<ChatFooter>
             child: GestureDetector(
               onTap: () {},
               child: Image.asset(
-                'assets/images/keyboard_mini.png',
+                'assets/images/keyboard_mini.png',package: 'ai_chat_assistant',
                 width: 24,
                 height: 24,
               ),