readme: add location- to leaderboard in subdomain
readme: add location- to leaderboard in subdomain

JaredKerim-Mozilla/leaderboard-server,JaredKerim-Mozilla/leaderboard-server,JaredKerim-Mozilla/leaderboard-server,mozilla-services/location-leaderboard,JaredKerim-Mozilla/leaderboard-server,mozilla-services/location-leaderboard,mozilla-services/location-leaderboard,JaredKerim-Mozilla/leaderboard-server,mozilla-services/location-leaderboard,mozilla-services/location-leaderboard