Add Face Mask Detection using YoloV4

[NEERAJAP2001]

Alert System: It monitors the mask, no-mask counts and has 3 status :

• Safe : When all people are with mask.
• Warning : When atleast 1 person is without mask.
• Danger : When some ratio of people are without mask.
  Details of model will be given in the Readme File

I'd like to work as part of gssoc21