Resolve "Add documentation for AR/VR synchronization"

What does this MR do?

Almost one year ago, a new design was proposed to synchronize efficiently the process of video frames with AR. This was tested in ExSimpleARCV but not documented.

This MR is an attempt to create some documentation for a basic AR application, which includes this question of synchronization.

How to test it?

• make html
• Open the documentation and check it !

Associated Issues/Merge Requests

• Issues

  • Closes #24 (closed)

• Merge requests

  • Sight/sight!142