[css-nav-1] Update metadata

This is a csswg spec now, update metadata accordingly

Author: frivoal

css-nav-1/Overview.bs

@@ -1,11 +1,13 @@
 <pre class='metadata'>
 Title: Spatial Navigation
-Shortname: spatnav
+Shortname: css-nav
 Level: 1
 Status: ED
-Group: WICG
+Work Status: exploring
+Group: csswg
 Repository: wicg/spatial-navigation
-URL: http://wicg.github.io/spatial-navigation
+ED: https://drafts.csswg.org/css-nav-1/
+Issue Tracking: Old issues (prior to the migration from WICG) https://github.com/WICG/spatial-navigation/issues?q=is%3Aopen+is%3Aissue+label%3Atopic%3Aspec
 Editor: Jihye Hong, LG Electronics, jh.hong@lge.com
 Editor: Florian Rivoal, Invited Expert, https://florian.rivoal.net
 Abstract: This specification defines a general model for navigating the focus using the arrow keys,