docs: added Dependency Container documentation (#2439)

www/docs/sidebars.js

@@ -388,6 +388,10 @@ module.exports = {
           type: "doc",
           id: "advanced/backend/customer-groups/index"
         },
+        {
+          type: "doc",
+          id: "advanced/backend/dependency-container/index"
+        },
       ]
     },
     {