A shard is what we call a crystal library, and this is the website that lists them all.
To experiment with this, you can post this to your own heroku site.
You can read about Deploying to Heroku or just follow these steps:
NAME=crystal-shards-demo
heroku create $NAME --buildpack https://github.com/zamith/heroku-buildpack-crystal
git push heroku master