docs: "UNLICENSED" and "SEE LICENSE IN <filename>"

Fixes: #8557

PR-URL: #8609

doc/files/package.json.md

@@ -115,9 +115,9 @@ expression syntax version 2.0 string](http://npmjs.com/package/spdx), like this:
 If you are using a license that hasn't been assigned an SPDX identifier, or if
 you are using a custom license, use the following valid SPDX expression:
 
-    { "license" : "LicenseRef-LICENSE" }
+    { "license" : "SEE LICENSE IN <filename>" }
 
-Then include a LICENSE file at the top level of the package.
+Then include a file named `<filename>` at the top level of the package.
 
 Some old packages used license objects or a "licenses" property containing an
 array of license objects:
@@ -147,6 +147,13 @@ Those styles are now deprecated. Instead, use SPDX expressions, like this:
 
     { "license": "(MIT OR Apache-2.0)" }
 
+Finally, if you do not wish to grant others the right to use a private or
+unpublished package under any terms:
+
+    { "license": "UNLICENSED"}
+
+Consider also setting `"private": true` to prevent accidental publication.
+
 ## people fields: author, contributors
 
 The "author" is one person.  "contributors" is an array of people.  A "person"