doc: advise users to import the full set of trusted release keys

PR-URL: #32655
Fixes: #32559
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

README.md

@@ -602,7 +602,8 @@ Primary GPG keys for Node.js Releasers (some Releasers sign with subkeys):
 * **Shelley Vohr** <shelley.vohr@gmail.com>
 `B9E2F5981AA6E0CD28160D9FF13993A75599653C`
 
-To import the full set of trusted release keys:
+To import the full set of trusted release keys (including subkeys possibly used
+to sign releases):
 
 ```bash
 gpg --keyserver pool.sks-keyservers.net --recv-keys 4ED778F539E3634C779C87C6D7062848A1AB005C