title: vulkan extension : which are supported by whom?
body: <p>There is <code>EXT</code>, <code>KHR</code> or <code>AMD</code> or <code>NV</code> extensions. Maybe there are some others. I know that <code>NV</code> means <code>Nvidia</code> and that it nv extensions are unlikely supported by AMD. But what about khr ones or ext ones? Are they mandatory supported by everyone?</p>