import required library

Importing the required `os `python library to remediate this error as seen in logs -
```
File "app.py", line 26, in <module>
is_spaces = True if "SPACE_ID" in os.environ else False
NameError: name 'os' is not defined
```

app.py

@@ -12,6 +12,7 @@ import argparse
 import imageio
 import numpy as np
 import gradio as gr
+import os
 from PIL import Image
 from subprocess import PIPE, run