HDRenderLoop: Add k_identity4x4

Author: sebastienlagarde

Assets/ScriptableRenderLoop/ShaderLibrary/Common.hlsl

@@ -283,6 +283,7 @@ const float3x3 k_identity3x3 = {1.0, 0.0, 0.0,
                                 0.0, 1.0, 0.0,
                                 0.0, 0.0, 1.0};
 
+const float4x4 k_identity4x4 = {1.0, 0.0, 0.0, 0.0,
                                 0.0, 1.0, 0.0, 0.0,
                                 0.0, 0.0, 1.0, 0.0,
                                 0.0, 0.0, 0.0, 1.0 };