typedef uint16_t SkGlyphID

This goes well with our existing `typedef int32_t SkUnichar`.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2095263003

Review-Url: https://codereview.chromium.org/2095263003
diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 2795574..deb2819 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -348,6 +348,10 @@
 */
 typedef int32_t SkUnichar;
 
+/** 16 bit unsigned integer to hold a glyph index
+*/
+typedef uint16_t SkGlyphID;
+
 /** 32 bit value to hold a millisecond duration
  *  Note that SK_MSecMax is about 25 days.
  */