doc: mention the need to use compatibility version of FindCorrade.cmake.
doc: mention the need to use compatibility version of FindCorrade.cmake.

ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,ashimidashajia/magnum,ashimidashajia/magnum,DerThorsten/magnum,ashimidashajia/magnum