Merge pull request KhronosGroup#2121 from Keenuts/licenses

adds Khronos license to LICENSES folder.

.reuse/dep5

@@ -8,4 +8,4 @@ License: Apache-2.0
 
 Files: spirv.h spirv.hpp GLSL.std.450.h
 Copyright: 2016-2021 The Khronos Group, Inc.
-License: MIT
+License: LicenseRef-KhronosFreeUse

LICENSES/LicenseRef-KhronosFreeUse.txt

@@ -0,0 +1,23 @@
+Copyright (c) 2014-2020 The Khronos Group Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and/or associated documentation files (the "Materials"),
+to deal in the Materials without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Materials, and to permit persons to whom the
+Materials are furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Materials.
+
+MODIFICATIONS TO THIS FILE MAY MEAN IT NO LONGER ACCURATELY REFLECTS KHRONOS
+STANDARDS. THE UNMODIFIED, NORMATIVE VERSIONS OF KHRONOS SPECIFICATIONS AND
+HEADER INFORMATION ARE LOCATED AT https://www.khronos.org/registry/
+
+THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM,OUT OF OR IN CONNECTION WITH THE MATERIALS OR THE USE OR OTHER DEALINGS
+IN THE MATERIALS.