DNS does not allow CNAME records at an apex domain (e.g. kernelkit.org),
so GitHub Pages cannot reliably redirect kernelkit.github.io to it. A
www subdomain can carry a CNAME pointing directly to kernelkit.github.io,
giving GitHub full control over the mapping and making the redirect work.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>