Make clear that the carbon footprint numbers are computed using France as a base

[Flaburgan]

Data used in the game are coming for the ADEME, a french agency working on energy and climate change.
Make clear that the numbers used in the game are true only for France. That is important for topics like carbon footprint of exotic fruits, or especially for the electricity footprint, as France has a one of the lowest carbon electricity grid in the world. So numbers would be very different in other countries, especially the ones using coal power plants.