docs: document new zink-flag
We forgot to document this previously, so let's add it now.
Fixes: feb9462b ("zink: Added inbuilt debug logging from the VK_LAYER_LUNARG_standard_validation layer.")
We forgot to document this previously, so let's add it now.
Fixes: feb9462b ("zink: Added inbuilt debug logging from the VK_LAYER_LUNARG_standard_validation layer.")