Add project page for playground

The Fathom Playground is the self-directed learning program we want to launch to bootstrap the fathom network. It is built around a small set of rules and uses the chatrooms.

This MR is adding a project sections to the homepage. Currently the only project would be The Playground but we should also add one for the chatrooms.

The project page should explain what exactly the project is, not necessarily be a marketing page for it. The goal is to split it into it's component parts and give a high level overview on the main-page, and then explore each component