Add a function that retrieves query string values

[dominictwlee]

Hi Kent, thank you so much for helping us newbies get our feet wet in open source!

I'd like to add a function that retrieves query string values.

https://stackoverflow.com/questions/901115/how-can-i-get-query-string-values-in-javascript/901144#901144

[kentcdodds]

Looks super! Thanks @dominictwlee!