Interface layout update

Included an extra button and changed the theme.

app.py

@@ -36,7 +36,7 @@ with gr.Blocks() as demo:
     """)
 
   chatbot = gr.Chatbot()
-  msg = gr.Textbox()
+  msg = gr.Textbox(label= "Chat", default = "Introduce tu pregunta")
   with gr.Row():
     btn = gr.Button(value="Submit")
     clear = gr.Button("Clear")