DOC: Provide project site URL for the website
DOC: Provide project site URL for the website

https://github.com/fmrchallenge/fmrbenchmark-website/

It is already referenced in the footer of the deployed website. Also
providing it in the README makes it is easier to find if someone
(initially) has only the source code.

fmrchallenge/fmrbenchmark-website,fmrchallenge/fmrbenchmark-website,fmrchallenge/fmrbenchmark-website