We need a high level whitepaper explaining how matrix works

From https://matrix.org/jira/browse/ORG-24:

> We already have the bloggeek.me and LWN article, and need to write something for webrtchacks too. Whatever the channel, having a nice technical-journalism style article that we've written ourselves describing how Matrix works would be useful.

Start by reviewing the linked ORG-24 request and the existing bloggeek.me and LWN articles mentioned in the issue. Define a high-level technical-journalism article explaining how Matrix works, with wording suitable for publication through a channel such as webrtchacks; done means the article is complete and ready for publication.

Written by the indexing model from the issue text.