doc: clarify moderation in onboarding.md

This change gives more attention to moderation requirements
collaborators can perform as part of the onboarding process.

PR-URL: https://github.com/nodejs/node/pull/41930
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Michael Dawson <midawson@redhat.com>

onboarding.md

@@ -108,8 +108,15 @@ The project has a venue for real-time discussion:
   * This is a repository to which all members of the `nodejs` GitHub
     organization (not just collaborators on Node.js core) have access. Its
     contents should not be shared externally.
-  * You can find the full moderation policy
-    [here](https://github.com/nodejs/admin/blob/HEAD/Moderation-Policy.md).
+  * Node.js has a moderation team which you should contact when unsure
+    about taking action in the Node.js org.
+  * You can moderate non-collaborator posts yourself. Please
+    report the moderation action taken in accordance to the moderation
+    policy.
+  * You can always refer to the
+    [full moderation policy](https://github.com/nodejs/admin/blob/main/Moderation-Policy.md).
+  * You can contact someone in the
+    [full list of moderation team members](https://github.com/nodejs/moderation#moderation-team-members).
 
 ## Reviewing pull requests