Support position: sticky

Author: kazzarin

src/css/Properties.js

@@ -378,7 +378,7 @@ var Properties = module.exports = {
     "pitch-range"                       : 1,
     "play-during"                       : 1,
     "pointer-events"                    : "auto | none | visiblePainted | visibleFill | visibleStroke | visible | painted | fill | stroke | all",
-    "position"                          : "static | relative | absolute | fixed",
+    "position"                          : "static | relative | absolute | fixed | sticky",
     "presentation-level"                : 1,
     "punctuation-trim"                  : 1,