The website advertises a favicon in PNG format, but we don't actually
provide one. From docs/website/header.html:
<link rel="shortcut icon" href="images/favicon.png">
So add one. Generated by:
convert -geometry 32x32! docs/website/images/logo_small.png \
docs/website/favicon.png
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
