Update app.py

Adding a new sample to the list of samples on the space demo

app.py

@@ -79,6 +79,7 @@ if __name__ == "__main__":
                 os.path.join(os.path.curdir, "examples", "sample1.jpg"),
                 os.path.join(os.path.curdir, "examples", "sample2.jpg"),
                 os.path.join(os.path.curdir, "examples", "sample3.jpg"),
+                os.path.join(os.path.curdir, "examples", "sample4.png")
             ],
             inputs=image_input,
             outputs=lbl_output,