doc: add policy for “placeholder” executables

doc/contributing/distribution.md

@@ -25,3 +25,18 @@ only as a semver-major change, unless the related feature or project is
 documented as experimental. In addition, Node.js includes external projects as
 internal dependencies. These may be replaced or removed at any time, provided
 that doing so is not a breaking change.
+
+## Placeholder executables
+
+Installing Node.js will not create "placeholder" executables for package
+managers. A placeholder executable is a binary, symlink or script that has a
+name that refers to software that is not distributed with Node.js, but instead
+would be downloaded when the executable is run. For example, Node.js will not
+create `yarn` or `download_yarn` placeholder executables that will download Yarn
+when run. Node.js includes `npm` and `npx` executables, but these are not
+placeholders because the name of the executable refers to software that is
+contained within the Node.js distribution.
+
+Adding placeholder executables that refer to other types of software besides
+package managers will first require an affirmative vote of the Node.js Technical
+Steering Committee.