docs: prepare moving the website

This commit just creates a symlink so the website is now accessible from
both docs/ and docs/website/.

This allows us to have the website now officially in docs/website, while
still keep backward compatibility with the current scripts that update
the website. Once those scripts have been updated, we'll be able to truly
move the website to docs/website/ for good.

All without any perceived downtime or missed updated on the website! :-)

After an idea from Peter.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Peter Korsgaard <jacmet@uclibc.org>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>