Add Vulkan specific header.txt

Author: Exanite

eng/silktouch/vulkan/header.txt

@@ -0,0 +1,5 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Ported from the Vulkan headers and corresponding dependencies.
+// Original source is Copyright 2015-2023 The Khronos Group Inc. Licensed under the MIT license.

eng/silktouch/vulkan/settings.rsp

@@ -2,7 +2,7 @@
 --define-macro
 TODO_DEFINE_MACROS=HERE
 --headerFile
-../../header.txt
+../header.txt
 --include-directory
 ../../../submodules/vulkan-headers/include
 --with-callconv