fix: nav type

types/default-theme.d.ts

@@ -86,12 +86,14 @@ export namespace DefaultTheme {
     activeMatch?: string
   }
 
-  export interface NavItemWithChildren {
+  export type NavItemChildren = {
-    text?: string
-    items: {
     text?: string
     items: NavItemWithLink[]
-    }[]
+  }
+
+  export interface NavItemWithChildren {
+    text?: string
+    items: (NavItemChildren | NavItemWithLink)[]
   }
 
   // sidebar -------------------------------------------------------------------