refactor(blog): Move most content to a single directory

app/site.hs

content/404.html

content/about.html

content/favicon.ico

content/images/avatar.jpeg

content/images/doge.png

content/images/ensure-banner.png

content/images/header_logo_float.png

content/images/markdown-mark.svg

content/images/posts/2017-redesign.jpg

content/images/posts/POODLE.png

content/images/posts/ensure-logo.png

content/images/posts/foundation-checkbox.png

content/images/posts/gentoo-partitions.svg

content/images/posts/gentoo-screenfetch.png

content/images/posts/haddocks.png

content/images/posts/haskell-containers.png

content/images/posts/hypercube.png

content/images/posts/legit-logo.png

content/images/posts/networkmanager-vpn.png