Inside Ultralytics video https://youtu.be/Zgi9g1ksQHc (#5546)

* Update detect.py Usage examples

* Inside Ultralytics at https://youtu.be/Zgi9g1ksQHc

detect.py

@@ -3,7 +3,13 @@
 Run inference on images, videos, directories, streams, etc.
 
 Usage:
-    $ python path/to/detect.py --source path/to/img.jpg --weights yolov5s.pt --img 640
+    $ python path/to/detect.py --weights yolov5s.pt --source 0  # webcam
+                                                             img.jpg  # image
+                                                             vid.mp4  # video
+                                                             path/  # directory
+                                                             path/*.jpg  # glob
+                                                             'https://youtu.be/Zgi9g1ksQHc'  # YouTube
+                                                             'rtsp://example.com/media.mp4'  # RTSP, RTMP, HTTP stream
 """
 
 import argparse