doc(toc): add missing shadows entry (backport #827) (#829)

Co-authored-by: xiaoy312 <[email protected]>

Author: mergify[bot]

doc/toc.yml

@@ -40,6 +40,8 @@
       href: controls/NavigationBar.md
     - name: SafeArea
       href: controls/SafeArea.md
+    - name: ShadowContainer
+      href: controls/ShadowContainer.md
     - name: TabBar and TabBarItem
       href: controls/TabBarAndTabBarItem.md
   # ***************** Reference\Helpers *******************
@@ -63,4 +65,4 @@
   - name: Styles
     href: controls-styles.md
   - name: Migrate to Uno Material v2
-    href: material-migration.md
+    href: material-migration.md