Add kbr as code owner. Requesting this permission mainly to be able to unblock CLs in areas of expertise like the Mac port. Bug: angleproject:6769 Change-Id: I2b50b26d868c14ac788bccec5b1106627bf9df57 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3319341 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Kenneth Russell <kbr@chromium.org>