Add codeowners

Generally owned by the Glean team, with server-side events implementation handled by @akkomar

.github/CODEOWNERS

@@ -0,0 +1,12 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This CODEOWNERS file defines individuals or teams that are responsible
+# for code in this repository.
+# See https://help.github.com/articles/about-codeowners/ for details.
+
+* @mozilla/glean
+glean_parser/*_server.py @akkomar
+tests/*_server.py @akkomar
+server_telemetry/* @akkomar