Add myself to headless/OWNERS

Change-Id: Ibbcdcb6f036ee0ab185558bb437542f556658176
Reviewed-on: https://chromium-review.googlesource.com/1148644Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577606}

headless/OWNERS

@@ -4,6 +4,7 @@ eseckler@chromium.org
 # PST
 dgozman@chromium.org
 pfeldman@chromium.org
+caseq@chromium.org
 
 # Emeritus:
 altimin@chromium.org