Merge pull request #33113 from backstage/rugvip/docs-frontend-plugin-installation

docs: default frontend plugin docs to the new frontend system

microsite/sidebars.ts

@@ -560,15 +560,15 @@ export default {
         ),
         sidebarElementWithIndex(
           {
-            label: 'New Frontend System',
-            description: 'New frontend system components and architecture.',
+            label: 'Frontend System',
+            description: 'Frontend system components and architecture.',
           },
           [
             'frontend-system/index',
             sidebarElementWithIndex(
               {
                 label: 'Architecture',
-                description: 'Architecture of the new frontend system.',
+                description: 'Architecture of the frontend system.',
                 differentiator: 'frontend-system/',
               },
               [
@@ -606,6 +606,7 @@ export default {
               },
               [
                 'frontend-system/building-apps/index',
+                'frontend-system/building-apps/installing-plugins',
                 'frontend-system/building-apps/configuring-extensions',
                 'frontend-system/building-apps/built-in-extensions',
                 'frontend-system/building-apps/plugin-conversion',