npm-adduser: add page (#14418)

pages/common/npm-adduser.md

@@ -0,0 +1,20 @@
+# npm adduser
+
+> Add a registry user account.
+> More information: <https://docs.npmjs.com/cli/npm-adduser>.
+
+- Create a new user in the specified registry and save credentials to `.npmrc`:
+
+`npm adduser --registry={{registry_url}}`
+
+- Log in to a private registry with a specific scope:
+
+`npm login --scope={{@mycorp}} --registry={{https://registry.mycorp.com}}`
+
+- Log out from a specific scope and remove the auth token:
+
+`npm logout --scope={{@mycorp}}`
+
+- Create a scoped package during initialization:
+
+`npm init --scope={{@foo}} {{--yes}}`