doc: Describe the new Advertisement Monitor support

doc: Describe the new Advertisement Monitor support

This describes the following commands and event.
- Read Advertisement Monitor Features command
- Add Advertisement Patterns Monitor command
- Remove Advertisement Monitor command
- Advertisement Monitor Added event
- Advertisement Monitor Removed event
Note that the content of a monitor can differ based on its type. For now we
introduce only pattern-based monitor, so you may find that unlike the
command of removing monitor(s), the Add command is tied to a specific type.

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>