WIP: VLM Example: Mosaic

Hello mentors :)

This file explains how to create and play/stream a Mosaic using the VLM files. This took a little longer than I anticipated.

I would like to ask for your feedback for the file, and if the graph is alright. As I am a little new to the functioning of a mosaic, I would also request for a feedback over how accurate the explanations is.

advanced/vlm/index.rst

+##########################
+ VideoLAN Manager
+##########################
+
+.. toctree::
+   :maxdepth: 2
+
+   vlm_mosaic.rst