Action nodes support and lots of other updates

resources/shaderlib/RTSLib_Colour.glsl

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+// This file is part of the OGRE project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at https://www.ogre3d.org/licensing.
+// SPDX-License-Identifier: MIT
+
+#ifdef USE_LINEAR_COLOURS
+#define ENABLE_LINEAR_COLOUR(colour) colour.rgb = pow(colour.rgb, vec3_splat(2.2))
+#else
+#define ENABLE_LINEAR_COLOUR(colour)
+#endif
+
+#if defined(USE_LINEAR_COLOURS) && !defined(TARGET_CONSUMES_LINEAR)
+#define COLOUR_TRANSFER(colour) colour.rgb = pow(colour.rgb, vec3_splat(1.0/2.2))
+#else
+#define COLOUR_TRANSFER(colour)
+#endif