Add @Totktonada as codeowner for config

I want to receive review request notifications about the changes and let
people know who is responsible to accept them.

NO_CHANGELOG=no code changes
NO_TEST=no code changes
NO_DOC=no code changes

.github/CODEOWNERS

@@ -5,3 +5,7 @@
 /test/       @tarantool/devx
 /.test.mk    @tarantool/devx
 /test-run/   @tarantool/devx
+# Alexander Turenko wants to track all the activities around the
+# declarative configuration.
+/src/box/lua/config/  @Totktonada
+/test/config-luatest/ @Totktonada