wp-calypso/client/reader/onboarding/constants.tsx

export const READER_ONBOARDING_PREFERENCE_KEY = 'has_completed_reader_onboarding';
export const READER_ONBOARDING_SEEN_PREFERENCE_KEY = 'has_seen_reader_onboarding';
export const READER_ONBOARDING_TRACKS_EVENT_PREFIX = 'calypso_reader_onboarding_';