Clarify the need to setup Wordpress locally

I wanted to fix one thing on jquery.com and I didn't do anything there for a long time so I decided to try with freshly cloned repos with the new Vagrant setup. I started from:
https://github.com/jquery/jquery.com/blob/master/README.md
which redirects to:
https://github.com/jquery/jquery-wp-content
(basically just "install Virtualbox & Vagrant & run vagrant up" - simple) and:
http://contribute.jquery.org/web-sites/#workflow
However, it didn't work for me, I was getting wordpress-validate errors about and unknown error that may mean Wordpress or the database is not set properly. Now, instructions at the contribute url say:

Edit config.json to use the URL, username, and password for your local WordPress network

which may suggest you first need to set up the Wordpress instance... but with having most of the setup handled by Vagrant, I thought that's handled as well.

It would save me (& maybe more people) some time if a step saying explicitly about going to http://vagrant.jquery.com & setting it up first was introduced.