Updated GR-MANGO RZ/A2M Mbed samples to add the face detection sample program using OpenCV

Updated GR-MANGO RZ/A2M Mbed samples to add the face detection sample program using OpenCV.

After GR-MANGO detects a person without mask, It will surround the face of a person without a mask with a red rectangle and sound alarm at the same time.

Try No.24 of the project.

Note:

• Set "camera-type" value to "CAMERA_RASPBERRY_PI_832X480" in mbed_app.json.
• Copy the face-detection-data and alarm sound file to the root directory of a micro SD card or an USB Flash memory, and insert it to GR-MANGO.
• Use Mbed CLI to build this project. Because OpenCV library is for GCC_ARM compiler.