Publish style guide like other products

[mjang]

Overview

As a writer, I want easy access to the NGINX style guide, so I can:

• Refer to it as needed
• include instructions / links from it for others, without having to refer to the GitHub repo

Description

It's difficult for many to access the GitHub repo for style. In addition, published style guides have more credibility.

Acceptance criteria

A style guide accessible at a docs.nginx.com URL such as docs.nginx.com/style-guide

[mjang]

cc @ADubhlaoich . @jputrino suggested that you also want this. It would have made my life easier during Write the Docs writing day

[ADubhlaoich]

In a much broader sense, I actually want the entirety of our process documentation public as a unified contribution hub.