submit to chrome store

[hxrts]

I don't think the Toolkit needs to be filled out much more before submitting an alpha to the Chrome App Store, but there are a few things I think we should have in place.

• Logo asset - @edouerd already has something very nice in the works.
• Better Print Are.na interface - @callil suggested an interstitial that offered a few layout options and then linked to the appropriate external location.
• Fullscreen show Are.na - this is a tool which I think could work quite well presented on-site.
• README update - Including better language around what the toolkit is, as well as how people can get started making their own tools.
• Maybe some small UI adjustments to make things more unobtrusive, comments or PRs invited here.