Please add the `racket` topic to this repo

[spdegabrielle]

Hi ,
Please add the racket topic to this repo - I think others will be interested and this will help them find it at https://github.com/topics/racket

https://help.github.com/en/articles/classifying-your-repository-with-topics

Kind regards,

Stephen

[jackfirth]

Done, thank you!