initial work to split into dart_filament and flutter_filament

flutter_filament/windows/include/GLES3/.clang-format

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+DisableFormat: true
+SortIncludes: false

flutter_filament/windows/include/GLES3/gl3platform.h

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+#ifndef __gl3platform_h_
+#define __gl3platform_h_
+
+/*
+** Copyright 2017-2020 The Khronos Group Inc.
+** SPDX-License-Identifier: Apache-2.0
+*/
+
+/* Platform-specific types and definitions for OpenGL ES 3.X  gl3.h
+ *
+ * Adopters may modify khrplatform.h and this file to suit their platform.
+ * Please contribute modifications back to Khronos as pull requests on the
+ * public github repository:
+ *      https://github.com/KhronosGroup/OpenGL-Registry
+ */
+
+#include <KHR/khrplatform.h>
+
+#ifndef GL_APICALL
+#define GL_APICALL  KHRONOS_APICALL
+#endif
+
+#ifndef GL_APIENTRY
+#define GL_APIENTRY KHRONOS_APIENTRY
+#endif
+
+#endif /* __gl3platform_h_ */