docs: documet support for type aliases (#11117)

www/apps/book/sidebar.mjs

@@ -500,6 +500,17 @@ export const sidebar = sidebarAttachHrefCommonOptions([
     title: "Storefront Development",
     chapterTitle: "Storefront",
   },
+  {
+    type: "category",
+    title: "Conventions",
+    children: [
+      {
+        type: "link",
+        title: "Type Aliases",
+        path: "/learn/conventions/ts-aliases",
+      },
+    ],
+  },
   {
     type: "link",
     path: "/learn/debugging-and-testing",