Add a paragraph to explain how to export multiple textures allocated from the same VkDeviceMemory

[matlemuzic]

Hi, title says it all, I would like to export multiple textures allocated fron the same VkDeviceMemory, but when I try to offset the handle by the actual resource offset, opengl does not seem to be pleased with that, the only explanation I could find was from the VMA website explaing that GL requires a specific alignment, but that's pretty much all I could find, nothing on the actual alignment required by GL, a bit of clarity on this would be greatly appreciated, cheers. Link to the VMA doc: https://gpuopen-librariesandsdks.github.io/VulkanMemoryAllocator/html/opengl_interop.html