CODEOWNERS: Add myself as reviewer on security docs (#28216)

Signed-off-by: Russell Bryant <rbryant@redhat.com>

.github/CODEOWNERS

@@ -127,3 +127,8 @@ mkdocs.yaml @hmellor
 /vllm/config/pooler.py @noooop
 /vllm/pooling_params.py @noooop
 /vllm/model_executor/layers/pooler.py @noooop
+
+# Security guide and policies
+/docs/usage/security.md @russellb
+/SECURITY.md @russellb
+/docs/contributing/vulnerability_management.md @russellb