Add a note to event-log-tags listing the log tag range

# browser stats for diary study

70101 browser_zoom_level_change (start level|1|5),(end level|1|5),(time|2|3)

70102 browser_double_tap_duration (duration|1|3),(time|2|3)

# NOTE - the range 1000000-2000000 is reserved for partners and others who

# want to define their own log tags without conflicting with the core platform.