render/vulkan: support screencopy
Created by: David96
Currently when trying to take a screenshot with grim while using the vulkan renderer the following error happens:
00:00:15.573 [ERROR] [wlr] [render/vulkan/renderer.c:915] vulkan_preferred_read_format not implemented
00:00:15.589 [ERROR] [wlr] [render/vulkan/renderer.c:979] vulkan_read_pixels not implemented
Both functions already have a "TODO: implement" in the code but I thought it'd make sense to track it as an issue here as well.