[css-values-4] Add Jan2019 version to Previous Versions

Author: tabatkins

css-values-4/Overview.bs

@@ -7,7 +7,8 @@ Status: ED
 Work Status: Exploring
 ED: https://drafts.csswg.org/css-values-4/
 TR: https://www.w3.org/TR/css-values-4/
-Previous version: https://www.w3.org/TR/2018/WD-css-values-4-20181010/
+Previous Version: https://www.w3.org/TR/2019/WD-css-values-4-20190131/
+Previous Version: https://www.w3.org/TR/2018/WD-css-values-4-20181010/
 Editor: Tab Atkins, Google, http://xanthir.com/contact/, w3cid 42199
 Editor: fantasai, http://fantasai.inkedblade.net/contact, w3cid 35400
 Abstract: This CSS module describes the common values and units that CSS properties accept and the syntax used for describing them in CSS property definitions.