Invite @raghavkaul as maintainer (#2663)

- Add @raghavkaul as a CODEOWNERS file reviewer
- Update the CODEOWNERS file

[.github/CODEOWNERS]
- Add @raghavkaul to CODEOWNERS file

Signed-off-by: naveensrinivasan <[email protected]>

Author: naveensrinivasan

.github/CODEOWNERS

@@ -6,7 +6,7 @@
 # review when someone opens a pull request.
 # TODO(owners): For ease of management, this should eventually shift to a
 #               defined GitHub team instead of individual usernames
-* @azeemshaikh38 @justaugustus @laurentsimon @naveensrinivasan @spencerschrock
+* @azeemshaikh38 @justaugustus @laurentsimon @naveensrinivasan @spencerschrock @raghavkaul
 
 # Docs
 # TODO(owners): For ease of management, this should eventually shift to a