[css-typed-om] Make the Abstract use less complicated English.

Author: tabatkins

css-typed-om/Overview.bs

@@ -9,7 +9,7 @@ Previous Version: https://www.w3.org/TR/2017/WD-css-typed-om-1-20170801/
 Previous Version: https://www.w3.org/TR/2016/WD-css-typed-om-1-20160607/
 Shortname: css-typed-om
 Level: 1
-Abstract: Converting CSSOM value strings into meaningfully typed JavaScript representations and back can incur a significant performance overhead. This specification exposes CSS values as typed JavaScript objects to facilitate their performant manipulation.
+Abstract: Converting CSSOM value strings into meaningfully typed JavaScript representations and back can incur a significant performance overhead. This specification exposes CSS values as typed JavaScript objects, to make manipulating them both easier and more performant.
 Editor: Tab Atkins-Bittner, Google, http://xanthir.com/contact/, w3cid 42199
 Editor: François Remy, Microsoft, w3cid 53348
 Former Editor: Shane Stephens, shanestephens@google.com, w3cid 47691