docs: update readme

Author: e06084

README.md

@@ -150,7 +150,8 @@ Try Dingo on our online demo: [(Hugging Face)🤗](https://huggingface.co/spaces
 Try Dingo in local:
 
 ```shell
-python app_gradio/app.py
+cd app_gradio
+python app.py
 ```
 
 ![Gradio demo](docs/assets/gradio_demo.png)

README_ja.md

@@ -150,7 +150,8 @@ python -m dingo.run.vsl --input output_directory
 地元でDingoを試してみましょう：
 
 ```shell
-python app_gradio/app.py
+cd app_gradio
+python app.py
 ```
 
 ![Gradio demo](docs/assets/gradio_demo.png)

README_zh-CN.md

@@ -148,7 +148,8 @@ python -m dingo.run.vsl --input 输出目录
 尝试我们的本地演示：
 
 ```shell
-python app_gradio/app.py
+cd app_gradio
+python app.py
 ```
 
 ![Gradio demo](docs/assets/gradio_demo.png)