[FEAT] Azure AI Face service

[kavejo]

Please consider implementing the ability to use Azure AI Face service for face recognition/detection.
There are people who avail of free Azure credit that would benefit from leveraging these services to perform face recognition.

Ref: https://azure.microsoft.com/en-gb/products/ai-services/ai-vision/.

Or, if already implemented (as it might appear from jakowenko#303), please consider the opportunity to add documentation on how to configure it please.

Thanks!