Shell/4235

The companion piece to https://github.com/endlessm/gnome-user-docs/pull/11

Actually needs that pull request, as it relies on some of the assets in that repo. The two repos use a number of the same assets from design, and I could have made a copy of each under a different name in this repo, but that just seemed like a maintenance headache. So all the eos-* images and in user-docs with some references from this repo.

endlessm/eos-shell#4235]