Update readme.md
Update readme.md

Fix the plugin name
vhk/cordova-google-play-games-services-vhk,01org/cordova-google-play-games-services,jerejigga/cordova-google-play-games-services,tony--/cordova-google-play-games-services,jerejigga/cordova-google-play-games-services,tony--/cordova-google-play-games-services,creith/cordova-google-play-games-services,vhk/cordova-google-play-games-services-vhk,creith/cordova-google-play-games-services,01org/cordova-google-play-games-services