[svg] Add public API

* hb_ot_color_has_svg
* hb_ot_color_glyph_svg_create_blob

src/hb-ot-face.cc

diff --git a/src/hb-ot-face.cc b/src/hb-ot-face.cc
index 1bc68d3..0aba2a6 100644
--- a/src/hb-ot-face.cc
+++ b/src/hb-ot-face.cc
@@ -32,6 +32,8 @@
 #include "hb-ot-kern-table.hh"
 #include "hb-ot-post-table.hh"
 #include "hb-ot-color-cbdt-table.hh"
+#include "hb-ot-color-sbix-table.hh"
+#include "hb-ot-color-svg-table.hh"
 #include "hb-ot-layout-gdef-table.hh"
 #include "hb-ot-layout-gsub-table.hh"
 #include "hb-ot-layout-gpos-table.hh"