Add tier badge

Add Free tier badge to page.

doc/user/packages/package_registry/index.md

@@ -4,7 +4,7 @@ group: Package
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Package Registry
+# Package Registry **(FREE)**
 
 > [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/221259) to GitLab Free in 13.3.