A quick example to set up a monitor on a live stream (#127)

Add example live stream monitor to the docs

Author: paulina-positronix

docs/docs/getting-started/5-streaming.md

@@ -0,0 +1,74 @@
+# A Quick Example: Live Stream Alert 
+
+A quick example to get used to setting up detectors and asking good questions: set up a monitor on a live stream. 
+
+## Requirements
+
+- [Groundlight SDK](/docs/installation/) with Python 3.7 or higher
+- The video ID of a YouTube live stream you'd like to monitor
+
+## Installation
+
+Ensure you have Python 3.7 or higher installed, and then install the Groundlight SDK and OpenCV library:
+
+```bash
+pip install groundlight pillow ffmpeg yt-dlp typer
+```
+
+## Creating the Application
+
+1. Save this command as a shell script `get_latest_frame.sh`:
+
+```
+#!/bin/bash
+
+ffmpeg -i "$(yt-dlp -g $1 | head -n 1)" -vframes 1 last.jpg -y
+``` 
+
+This will download the most recent frame from a YouTube live stream and save it to a local file `last.jpg`. 
+
+2. Log in to the [Groundlight application](https://app.groundlight.ai) and get an [API Token](api-tokens).
+
+3. Next, we'll write the Python script for the application.
+
+```python notest
+import os
+import subprocess
+import typer
+from groundlight import Groundlight
+from PIL import Image
+
+
+def main(*, video_id: str = None, detector_name: str = None, query: str = None, confidence: float = 0.75, wait: int = 60):
+    """
+    Run the script to get the stream's last frame as a subprocess, and submit result as an image query to a Groundlight detector
+    :param video_id: Video ID of the YouTube live stream (the URLs have the form https://www.youtube.com/watch?v=<VIDEO_ID>)
+    :param detector_name: Name for your Groundlight detector
+    :param query: Question you want to ask of the stream (we will alert on the answer of NO)
+    """
+    gl = Groundlight()
+    detector = gl.create_detector(name=detector_name, query=query, confidence_threshold=confidence)
+
+    while True:
+        p = subprocess.run(["./get_latest_frame.sh", video_id])
+        if p.returncode != 0:
+            raise RuntimeError(f"Could not get image from video ID: {video_id}. Process exited with return code {p.returncode}.")
+        
+        image = Image.open("last.jpg").convert("RGB")
+        response = gl.submit_image_query(detector=detector, image=image, wait=wait)
+
+        if response.result.label == "NO":
+            os.system("say 'Alert!'") # this may not work on all operating systems
+
+
+if __name__ == "__main__":
+    typer.run(main)
+
+```
+
+4. Save the script as `streaming_alert.py` in the same directory as `get_latest_frame.sh` above and run it:
+
+```bash
+python streaming_alert.py <VIDEO_ID> --detector_name <DETECTOR_NAME> --query <QUERY IN QUOTATION MARKS>
+```
+