Add API test for hb_ot_color_get_color_layers
diff --git a/src/hb-ot-color.h b/src/hb-ot-color.h
index 0343e5e..62e873b 100644
--- a/src/hb-ot-color.h
+++ b/src/hb-ot-color.h
@@ -1,5 +1,7 @@
 /*
  * Copyright © 2016  Google, Inc.
+ * Copyright © 2018  Khaled Hosny
+ * Copyright © 2018  Ebrahim Byagowi
  *
  *  This is part of HarfBuzz, a text shaping library.
  *