home: move all custom CSS to dedicated CSS file

It's not really legal to have style-tags outside of the head-tag, even
though most browsers support it. Let's please the standard, and move
all of the home-page specific CSS definitions into a dedicated CSS file
for the homepage.

Acked-by: Eric Engestrom <eric@engestrom.ch>
5 jobs for master in 8 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #3541143
pages

00:00:08

 
  Deploy
passed pages:deploy

00:00:01

failed pages:deploy

00:00:00

failed pages:deploy

00:00:00

failed pages:deploy

00:00:00