Create a repository for CMCD information

[PCaponetti]

Currently, there is no central place where CMCD is described, or a repository of information about the topic.

There has been a proposal to use this GitHub repository to serve this purpose. Ideally, the Readme will have high level information, and potentially more in-depth information could be in the wiki.

[PCaponetti]

Possible interesting information: references to other projects, plugins, validators, talk recordings, how to activate it in common players, player availability.

Using the github repo README.

Maintenance could be a burden, possible unmaintained WIKI? Media profiles has a WIKI and finds great value in it.

Paul to take an inital pass at an updated readme.