It took me a while to figure out how best to put image heavy docs into a Wiki on
GitHub. Finally, gave up and moved these to a docs folder in Markdown syntax.
The images have been `pngcrush`ed with the `-brute` so they are about as small
as can be expected.
Added links to the articles from the README and also added Brandon's showcase to
zhoosh it up a bit :)
Fixes https://github.com/flutter/flutter/issues/104740