added an image save in text2image demo

user cant see the generated image because it doesnt display anywhere and is destroyed after the python context is over

README.md

@@ -59,6 +59,8 @@ prompt = "A photograph of the inside of a subway train. There are raccoons sitti
 
 generator = torch.Generator(device="cpu").manual_seed(0)
 image = pipe(prompt, num_inference_steps=25, generator=generator).images[0]
+
+image.save("kandinsky.png")
 ```
 
 ### Image-2-Image