Run cv2 window in fullscreen automatically

This is my code: (i saw in google but it doesn't work)

```
cv2.namedWindow(str(p), cv2.WINDOW_FULLSCREEN)  # allow window resize (Linux)
cv2.setWindowProperty(str(p), cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN)
cv2.resizeWindow(str(p), im0.shape[1], im0.shape[0])
```