rns the address of the specified Vulkan core or extension function for the specified instance. If instance is set to <code>NULL</code> it can return any function exported from the Vulkan loader, including at least the following functions:</p>
<ul>
<li><code>vkEnumerateInstanceExtensionProperties</code></li>
<li><code>vkEnumerateInstanceLayerProperties</code></li>
<li><code>vkCreateInstance</code></li>
<li><code>vkGetInstanceProcAddr</code></li>
</ul>
<p>If Vulkan is not available on the machine, this functi