[Myanmar] Add note re Uniscribe NOT applying 'mark'

src/hb-ot-shape-complex-myanmar.cc

@@ -120,6 +120,20 @@ static void
 override_features_myanmar (hb_ot_shape_planner_t *plan)
 {
   plan->map.add_feature (HB_TAG('l','i','g','a'), 0, true);
+
+  /*
+   * Note:
+   *
+   * Spec says 'mark' is used, and the mmrtext.ttf font from
+   * Windows 8 has lookups for it.  But testing suggests that
+   * Windows 8 Uniscribe is NOT applying it.  It *is* applying
+   * 'mkmk' however.
+   *
+   * We want to apply it, since that's the right thing to do.
+   */
+#if 0
+  plan->map.add_feature (HB_TAG('m','a','r','k'), 0, true);
+#endif
 }