npm: additional module listing use case (#1642)

pages/common/npm.md

@@ -23,10 +23,14 @@
 
 `npm uninstall {{module_name}}`
 
-- List a tree of installed modules:
+- List a tree of installed modules referenced in package.json:
 
 `npm list`
 
+- List top-level globally installed modules:
+
+`npm list -g --depth={{0}}`
+
 - Interactively create a package.json file:
 
 `npm init`