add client libraries for New Relic Browser

See: https://github.com/GigaOM/gigaom/issues/5525
I didn't know it was possible at the time I wrote the ticket, and I failed to mention it after, but we can set the app name here.

Not necessarily something we have to do right now, but [the app name logic elsewhere](https://github.com/zbtirrell/go-newrelic/blob/add-client/components/class-go-newrelic.php#L63) should probably be turned into a separate function so the app names here can conform.