It's super simple, you basically just have to checkout to your contribution branch from gh-pages
git checkout -b add/<project-name>
Then create a new file at _posts and add a preview image at assets/img/previews following the pattern:
file name: yyyy-mm-dd-<project-name>.md
file sctruture:
---
title: 'Snoop, the dog'
post_date: '9th December 2017'
image: 'assets/img/previews/snoop.png'
codepen: 'https://codepen.io/rmdias/pen/rpNpwB'
creator_name: 'Rodolfo Dias'
github_user: 'rmdias'
---
Note, the animation has to be hosted at codepen :)
And finally commit your changes using this commit message pattern:
add(showcase): <project-name>
This project is supported by all the contributors