URLSearchParams.get returns incorrect type

[SamWyld]

Currently the type of get in URLSearchParamsRe.re is:
[@bs.send.pipe : t] external get: string => option(string) = "";

As you can see in the documentation here

The type I think should be:
[@bs.send.pipe : t] external get: string => Js.Nullable.t(string) = "";

Quite happy to make a PR if I am correct about this :)

[glennsl]

Indeed it should, thanks! Closing in favor of #123.