Add doxygen group comments

...les/effects/include/vkcv/effects/BloomAndFlaresEffect.hpp

modules/effects/include/vkcv/effects/Effect.hpp

...es/effects/include/vkcv/effects/GammaCorrectionEffect.hpp

modules/tone_mapping/include/vkcv/tone/ACESToneMapping.hpp

modules/tone_mapping/include/vkcv/tone/FilmicToneMapping.hpp

modules/tone_mapping/include/vkcv/tone/LottesToneMapping.hpp

...s/tone_mapping/include/vkcv/tone/Reinhard2ToneMapping.hpp

...es/tone_mapping/include/vkcv/tone/ReinhardToneMapping.hpp

modules/tone_mapping/include/vkcv/tone/ToneMapping.hpp

...es/tone_mapping/include/vkcv/tone/UchimuraToneMapping.hpp

.../tone_mapping/include/vkcv/tone/Uncharted2ToneMapping.hpp

modules/tone_mapping/include/vkcv/tone/UnrealToneMapping.hpp