Update copyright headers

cmd/root.go

cmd/version.go

constants/constants.go

io/poll.go

main.go

notifications/apns/apns.go

notifications/ephemeral.go

notifications/ephemeral_test.go

notifications/firebase/fcm.go

notifications/firebase/fcm_test.go

notifications/ndf.go

notifications/ndf_test.go

notifications/notifications.go

notifications/notifications_test.go

storage/buffer.go

storage/buffer_test.go

storage/database.go

storage/databaseImpl.go

storage/mapImpl.go

storage/mapImpl_test.go