added face detection tutorial

Author: x4nth055

Diff for: README.md

@@ -19,6 +19,7 @@ This is a repository of all the tutorials of [The Python Code](https://www.thepy
 - ### [Machine Learning](https://www.thepythoncode.com/topic/machine-learning)
     - ### [Natural Language Processing](https://www.thepythoncode.com/topic/nlp)
         - [How to Build a Spam Classifier using Keras in Python](https://www.thepythoncode.com/article/build-spam-classifier-keras-python). ([code](machine-learning/nlp/spam-classifier))
+        - [How to Detect Human Faces in Python using OpenCV](https://www.thepythoncode.com/article/detect-faces-opencv-python). ([code](machine-learning/face_detection))
 
     - [Building a Speech Emotion Recognizer using Scikit-learn](https://www.thepythoncode.com/article/building-a-speech-emotion-recognizer-using-sklearn). ([code](machine-learning/speech-emotion-recognition))
     - [Top 8 Python Libraries For Data Scientists and Machine Learning Engineers](https://www.thepythoncode.com/article/top-python-libraries-for-data-scientists).

Diff for: machine-learning/face_detection/README.md

@@ -0,0 +1,5 @@
+# [How to Detect Human Faces in Python using OpenCV](https://www.thepythoncode.com/article/detect-faces-opencv-python)
+To run this:
+- `pip3 install -r requirements.txt`
+- If you want to detect faces in a sample image like `kids.jpg`, run `face_detection.py` script that generated another image `kids_detected.jpg` which contains rectangles around detected faces.
+- If you want to detect faces in your live cam, run `live_face_detection.py`