doc: add internal modules notice

Explicitly note that these modules should not be used outside of core.

PR-URL: https://github.com/nodejs/node/pull/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
new file mode 100644 (file)
index 0000000..38c7f6a
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+# 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.