doc: add internal modules notice

Fishrock123 · rvagg · commit d2ffecba2db7 · 2015-08-26T21:14:37.000+10:00
Explicitly note that these modules should not be used outside of core. PR-URL: #2523 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com> Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
diff --git a/lib/internal/readme.md b/lib/internal/readme.md
@@ -0,0 +1,4 @@
+# Internal Modules
+
+The modules in `lib/internal` are intended for internal use in Node.js core only, and are not accessible with `require()` from user modules.
+These are subject to change at **any** time. Reliance on these modules outside of core is **not supported** in any way.
