Add a tutorial to dweb primer based on the p2p-flipchart tutorial from mozfest

[flyingzumwalt]

see https://github.com/flyingzumwalt/decentralized-web-primer/issues/33

re-format the content of this tutorial using the structure of the dweb primer. This will make it easier to maintain and update over time. It also makes it easier to point people to specific parts of the tutorial if they have misunderstood something.

cc @diasdavid @pgte

[flyingzumwalt]

I forgot to add a link to the original tutorial!

• tutorial slides: https://www.slideshare.net/pgte/building-decentralised-realtime-collaborative-applications-building-google-docs-without-google