[Shader Language] Add missing token name.

servers/rendering/shader_language.cpp

@@ -128,6 +128,7 @@ const char *ShaderLanguage::token_names[TK_MAX] = {
 	"TYPE_USAMPLER3D",
 	"TYPE_SAMPLERCUBE",
 	"TYPE_SAMPLERCUBEARRAY",
+	"TYPE_SAMPLEREXT",
 	"INTERPOLATION_FLAT",
 	"INTERPOLATION_SMOOTH",
 	"CONST",