Returns a mapping between Unit categories and the uses they define.

Example

iex> Cldr.Unit.unit_category_usage
%{
  area: [:default, :geograph, :land],
  concentration: [:blood_glucose, :default],
  consumption: [:default, :vehicle_fuel],
  duration: [:default, :media],
  energy: [:default, :food],
  length: [:default, :focal_length, :person, :person_height, :rainfall, :road,
   :snowfall, :vehicle, :visiblty],
  mass: [:default, :person],
  mass_density: [:default],
  power: [:default, :engine],
  pressure: [:baromtrc, :default],
  speed: [:default, :wind],
  temperature: [:default, :weather],
  volume: [:default, :fluid, :oil, :vehicle],
  year_duration: [:default, :person_age]
}