add CONTRIBUTING, CoC, update License, Style Guide

[raynamharris]

PR Checklist

• [x] Release label added
• [x] PR category label added
• [x] PR mergeable
• [x] Clean build logs
• [x] Linked related issues #531 #532

PR Description

This PRs adds a contributing file as per #531 .

Also added the dependent CoC and license files.

Also renamed the index.md file in the Website-Style-Guide directory so that the landing page for the website style guide is https://training.nih-cfde.org/en/latest/Website-Style-Guide/ instead of https://training.nih-cfde.org/en/latest/Website-Style-Guide/0index/

PR Preview

https://cfde-training-and-engagement--542.com.readthedocs.build/en/542/Website-Style-Guide/

Reviewer Checklist

• [x] spelling and grammar
• [x] functional links (inter and intra)

Timeline

June release

[github-actions[bot]]

Reviewer Checklist

• [ ] spelling and grammar
• [ ] functional links (inter and intra)
• [ ] accessible hyperlink text

[raynamharris]

started as an an update of the contributing file, ended with some updates to the rendered style guide

[jeremywalter]

Website Style Guide doesn't show up for me on the menus or TOC. I can see it rendered when I use the link up top, but that's because it explicitly names the page, otherwise it's hidden.

[raynamharris]

working as intended. various documents link to it, such as the contributing and read me files and the wiki. but, we don't need it in the main menu bar.