docs(v2): Docs refactoring and reorganization (#3831)

* stable refactor of plugins api documentation

* plugins sidebar not collapsed by default as small?

* theme docs reorg

* Refactor migration guide doc

* fix broken link

website/sidebars.js

@@ -31,7 +31,6 @@ module.exports = {
         'blog',
         'search',
         'deployment',
-        'guides/migrating-from-v1-to-v2',
       ],
     },
     {
@@ -39,12 +38,51 @@ module.exports = {
       label: 'Advanced Guides',
       items: ['using-plugins', 'using-themes', 'presets'],
     },
+    {
+      type: 'category',
+      label: 'Migrating from v1 to v2',
+      items: [
+        'migration/migration-overview',
+        'migration/migration-automated',
+        'migration/migration-manual',
+        'migration/migration-versioned-sites',
+        'migration/migration-translated-sites',
+      ],
+    },
   ],
   api: [
     'cli',
     'docusaurus-core',
     'api/docusaurus.config.js',
     'lifecycle-apis',
-    'theme-classic',
+    {
+      type: 'category',
+      label: 'Plugins',
+      items: [
+        'api/plugins/plugins-overview',
+        'api/plugins/plugin-content-docs',
+        'api/plugins/plugin-content-blog',
+        'api/plugins/plugin-content-pages',
+        'api/plugins/plugin-client-redirects',
+        'api/plugins/plugin-debug',
+        'api/plugins/plugin-google-analytics',
+        'api/plugins/plugin-google-gtag',
+        'api/plugins/plugin-ideal-image',
+        'api/plugins/plugin-pwa',
+        'api/plugins/plugin-sitemap',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Themes',
+      items: [
+        'api/themes/themes-overview',
+        'api/themes/theme-configuration',
+        'api/themes/theme-classic',
+        'api/themes/theme-bootstrap',
+        'api/themes/theme-live-codeblock',
+        'api/themes/theme-search-algolia',
+      ],
+    },
   ],
 };