feat(admin): add custom admin route ranking feature (#13946)

* ✨ Add custom admin routes ranking

* 🐛 Fix sorting

* 📝 Update admin ui-routes documentation

* ✅ Add admin menu items spec

* 🔧 Add changeset

* 🐛 Remove redundant undefined initializations

* 🔥 🔥 Move the documentation to a separate PR

* ♻️ Move sorting logic to utils

* 🔧 Update changeset

---------

Co-authored-by: Bastien MONTOIS <bqst@bqst-hqckintosh.home>

.changeset/metal-lamps-film.md

@@ -0,0 +1,7 @@
+---
+"@medusajs/admin-vite-plugin": patch
+"@medusajs/admin-sdk": patch
+"@medusajs/dashboard": patch
+---
+
+feat(dashboard): add custom admin route ranking feature