Add OpenAI Codex npm host requirements to coding agent allowlist docs (#60061)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: timrogers <116134+timrogers@users.noreply.github.com>
Co-authored-by: Tim Rogers <timrogers@github.com>
Co-authored-by: hubwriter <hubwriter@github.com>

Author: 3 people

data/reusables/copilot/coding-agent-required-hosts.md

@@ -2,4 +2,10 @@
 * `user-images.githubusercontent.com`
 * `api.individual.githubcopilot.com` (if you expect {% data variables.copilot.copilot_pro_short %} or {% data variables.copilot.copilot_pro_plus_short %} users to use {% data variables.copilot.copilot_coding_agent %} in your repository)
 * `api.business.githubcopilot.com` (if you expect {% data variables.copilot.copilot_business_short %} users to use {% data variables.copilot.copilot_coding_agent %} in your repository)
-* `api.enterprise.githubcopilot.com` (if you expect {% data variables.copilot.copilot_enterprise_short %} users to use {% data variables.copilot.copilot_coding_agent %} in your repository)
+* `api.enterprise.githubcopilot.com` (if you expect {% data variables.copilot.copilot_enterprise_short %} users to use {% data variables.copilot.copilot_coding_agent %} in your repository)
+* If you are using the {% data variables.product.prodname_openai_codex %} third-party agent (for more information, see [AUTOTITLE](/copilot/concepts/agents/about-third-party-agents)):
+  * `npmjs.org`
+  * `npmjs.com`
+  * `registry.npmjs.com`
+  * `registry.npmjs.org`
+  * `skimdb.npmjs.com`