Allow optional usage of vulkan module

[Stef-2]

Given that vulkan-hpp now offers a module unit instead of a set of traditional header files, it would be very useful if either vma-hpp could do the same, or perhaps provide a DEFINE that would utilize the vulkan module over its very lengthy headers, as this can drastically reduce compile times.

[Arthapz]

or better, provide a vma C++ module

[YaaZ]

Please take a look and let me know how does it work for you.