cfgrib installation requires additional conda command

[GratienDSX]

Installing meteole works fine.

Problem arise when one tries to use AromeForecast or ArpegeForecast: it says ValueError: unrecognized engine cfgrib must be one of: ['scipy', 'rasterio', 'store']

After some digging we come to realize that simply running conda install -c conda-forge cfgrib allows for a proper installation of cfgrib. Indeed it requires ecCodes that isn't well handled by pip as it is not a pure python dependency.

Solution is straighforward (see above) for conda envs, but needs to be generalized.