doc: update guidance for adding new modules

- updated based on decision to use node: prefix in
  nodejs/TSC#1206
- updated based on agreement in TSC meeting
  on adding /promises to existing modules as per
  minutes - nodejs/TSC#1281

Signed-off-by: Michael Dawson <mdawson@devrus.com>

PR-URL: #44576
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Beth Griggs <bethanyngriggs@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Danielle Adams <adamzdanielle@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: mhdawson

doc/contributing/collaborator-guide.md

@@ -392,13 +392,21 @@ metadata. Raise a pull request like any other change.
 
 Treat commits that introduce new core modules with extra care.
 
-Check if the module's name conflicts with an existing ecosystem module. If it
-does, choose a different name unless the module owner has agreed in writing to
-transfer it.
+New modules must only be added with the `node:` prefix.
 
-If the new module name is free, register a placeholder in the module registry as
-soon as possible. Link to the pull request that introduces the new core module
-in the placeholder's `README`.
+When adding promises to an existing API, add `/promises`
+(`inspector/promises`, etc.). Apply the `semver-major` label to the addition.
+
+If the new module name is free in npm, register
+a placeholder in the module registry as soon as possible. Link to the pull
+request that introduces the new core module in the placeholder's `README`.
+
+If the module name is not free and the module is
+not widely used, contact the owner to see if they would be willing to transfer
+it to the project.
+
+We register a placeholder without the `node:` prefix whenever
+possible to avoid confusion and typosquatting attacks.
 
 For pull requests introducing new core modules: