GDScript: Add raw string literals (r-strings)

modules/gdscript/editor/gdscript_highlighter.h

@@ -78,6 +78,7 @@ private:
 	Color built_in_type_color;
 	Color number_color;
 	Color member_color;
+	Color string_color;
 	Color node_path_color;
 	Color node_ref_color;
 	Color annotation_color;