Add a `rank` property to each emoji object.

[zeke]

👋

@mroth would you open to adding a rank or ranking property using the data from http://emojitracker.com/api/rankings? It could be added at build time by hitting the webservice directly, or it could include the emoji-rankings package as devDependency.

Just wanted to see if you're game before I bother working on a PR for it.

[teedie8]

https://github.com/ummoji/emoji-rankings/blob/master/rankings.json

[zeke]

Thanks, @teedie8! I wrote that module. :)