[css-transitions-2] Add Brian Birtles as editor

Author: birtles

css-transitions-2/Overview.bs

@@ -25,6 +25,7 @@ Level: 2
 Group: csswg
 ED: https://drafts.csswg.org/css-transitions-2/
 Editor: L. David Baron, Mozilla https://www.mozilla.org/, https://dbaron.org/, w3cid 15393
+Editor: Brian Birtles, Invited Expert, brian@birchill.co.jp, w3cid 43194
 Issue Tracking: Bugzilla bugs for all levels https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Transitions&resolution=---
 Abstract: CSS Transitions allows property changes in CSS values to occur smoothly over a specified duration.
 Ignored Terms: translate, rotate, scale