aider: Added hello world Gradio app in `app.py`.

# Aider chat conversation:

USER: Make a hello world Gradio app in `app.py`

ASSISTANT: Sure, I will create a simple Gradio app that displays "Hello, World!" when run.

Here is the code:

```python
app.py
<<<<<<< HEAD

=======
import gradio as gr

def greet():
return "Hello, World!"

iface = gr.Interface(fn=greet, inputs=[], outputs="text")
iface.launch()
>>>>>>> updated
```

This code creates a Gradio interface with no inputs and a text output. The function `greet` returns the string "Hello, World!". The interface is then launched with `iface.launch()`. When you run this script, it will start a web server and print a URL you can visit in your web browser to interact with the app.

app.py

@@ -0,0 +1,7 @@
+import gradio as gr
+
+def greet():
+    return "Hello, World!"
+
+iface = gr.Interface(fn=greet, inputs=[], outputs="text")
+iface.launch()