Documentation work

Related to #2113
Related to #2120

docs/vulkan.dox

@@ -37,8 +37,8 @@ By default, GLFW will load the Vulkan loader dynamically at runtime via its stan
 `vulkan-1.dll` on Windows, `libvulkan.so.1` on Linux and other Unix-like systems and
 `libvulkan.1.dylib` on macOS.
 
-@macos GLFW will also look up and search the executable subdirectory of your application
-bundle.
+@macos GLFW will also look up and search the `Frameworks` subdirectory of your
+application bundle.
 
 If your code is using a Vulkan loader with a different name or in a non-standard location
 you will need to direct GLFW to it.  Pass your version of `vkGetInstanceProcAddr` to @ref
@@ -188,6 +188,13 @@ check whether any extensions you wish to enable are already in the returned
 array, as it is an error to specify an extension more than once in the
 `VkInstanceCreateInfo` struct.
 
+@macos MoltenVK is (as of July 2022) not yet a fully conformant implementation
+of Vulkan.  As of Vulkan SDK 1.3.216.0, this means you must also enable the
+`VK_KHR_portability_enumeration` instance extension and set the
+`VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR` bit in the instance creation
+info flags for MoltenVK to show up in the list of physical devices.  For more
+information, see the Vulkan and MoltenVK documentation.
+
 
 @section vulkan_present Querying for Vulkan presentation support