[#56] Basic scene loading from assets

include/vkcv/Image.hpp

modules/material/include/vkcv/material/Material.hpp

modules/material/src/vkcv/material/Material.cpp

modules/scene/CMakeLists.txt

modules/scene/include/vkcv/scene/Mesh.hpp

modules/scene/include/vkcv/scene/Node.hpp

modules/scene/include/vkcv/scene/Scene.hpp

modules/scene/src/vkcv/scene/Bounds.cpp

modules/scene/src/vkcv/scene/Mesh.cpp

modules/scene/src/vkcv/scene/Node.cpp

modules/scene/src/vkcv/scene/Scene.cpp

src/vkcv/Image.cpp

src/vkcv/ImageManager.cpp

src/vkcv/ImageManager.hpp