expand Join the Indieweb with icons etc like What is the IndieWeb

[tantek]

Per comment from @gRegorLove : Suggestion: a graphic for "Getting Started" on the homepage could be good - similar size as the heart icon on there. See discussion https://indiewebcamp.com/irc/2016-06-10#t1465582107200

I think this would be good for that entire section. We could even lay them out horizontally (as three icons with short text underneath each, side by side) rather than just another vertical layout, since less text is needed, and that matches what other "call to action" home page UIs have like http://habariproject.org/en/