[css-animations] Add birtles as co-editor.

As resolved in:
https://logs.csswg.org/irc.w3.org/css/2015-08-26/#e583324
with addition to WG recorded in:
https://lists.w3.org/Archives/Member/w3c-archive/2015Aug/0593.html

Author: dbaron

css-animations/Overview.bs

@@ -11,8 +11,9 @@ ED: http://dev.w3.org/csswg/css-animations/
 Previous Version: http://www.w3.org/TR/2013/WD-css3-animations-20130219/
 Previous Version: http://www.w3.org/TR/2012/WD-css3-animations-20120403/
 Editor: Dean Jackson, Apple Inc., dino@apple.com
-Editor: L. David Baron, Mozilla, dbaron@dbaron.org
+Editor: L. David Baron, Mozilla, http://dbaron.org/
 Editor: Tab Atkins Jr., Google, http://xanthir.com/contact/
+Editor: Brian Birtles, Mozilla Japan, bbirtles@mozilla.com
 Former Editor: David Hyatt, Apple Inc.
 Former Editor: Chris Marrin, Apple Inc.
 Former Editor: Sylvain Galineau, Adobe, galineau@adobe.com

css-animations/Overview.html

@@ -74,8 +74,9 @@ <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="cont
      <dd><a href="#issues-index">Inline In Spec</a>
      <dt class="editor">Editors:
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:dino@apple.com">Dean Jackson</a> (<span class="p-org org">Apple Inc.</span>)
-     <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:dbaron@dbaron.org">L. David Baron</a> (<span class="p-org org">Mozilla</span>)
+     <dd class="editor p-author h-card vcard"><a class="p-name fn u-url url" href="http://dbaron.org/">L. David Baron</a> (<span class="p-org org">Mozilla</span>)
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-url url" href="http://xanthir.com/contact/">Tab Atkins Jr.</a> (<span class="p-org org">Google</span>)
+     <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:bbirtles@mozilla.com">Brian Birtles</a> (<span class="p-org org">Mozilla Japan</span>)
      <dt>Former Editors:
      <dd>
       <dd class="editor p-author h-card vcard"><span class="p-name fn">David Hyatt</span> (<span class="p-org org">Apple Inc.</span>)