npm-{owner, author}: add page (#14605)

Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/common/npm-author.md

@@ -0,0 +1,7 @@
+# npm-author
+
+> This command is an alias of `npm owner`.
+
+- View documentation for the original command:
+
+`tldr npm owner`

pages/common/npm-owner.md

@@ -0,0 +1,16 @@
+# npm-owner
+
+> Manage ownership of published packages.
+> More information: <https://docs.npmjs.com/cli/commands/npm-owner>.
+
+- Add a new user as a maintainer of a package:
+
+`npm owner add {{username}} {{package_name}}`
+
+- Remove a user from a package's owner list:
+
+`npm owner rm {{username}} {{package_name}}`
+
+- List all owners of a package:
+
+`npm owner ls {{package_name}}`