[css-contain] Add Previous Version

Author: xfq

css-contain-1/Overview.bs

@@ -7,6 +7,7 @@ Work Status: completed
 Group: csswg
 ED: https://drafts.csswg.org/css-contain-1/
 TR: https://www.w3.org/TR/css-contain-1/
+Previous Version: https://www.w3.org/TR/2019/PR-css-contain-1-20191015/
 Previous Version: https://www.w3.org/TR/2019/CR-css-contain-1-20190430/
 Previous Version: https://www.w3.org/TR/2018/CR-css-contain-1-20181108/
 Previous Version: https://www.w3.org/TR/2018/CR-css-contain-1-20180524/