fix(kit): support modern builds with extendWebpackConfig (#1055)

packages/kit/src/module/utils.ts

@@ -180,6 +180,13 @@ export interface ExtendWebpackConfigOptions extends ExtendConfigOptions {
    * @default true
    */
   client?: boolean
+  /**
+   * Install plugin on modern build
+   *
+   * @default true
+   * @deprecated Nuxt 2 only
+   */
+  modern?: boolean
 }
 
 export interface ExtendViteConfigOptions extends ExtendConfigOptions {}
@@ -216,6 +223,13 @@ export function extendWebpackConfig (
         fn(config)
       }
     }
+    // Nuxt 2 backwards compatibility
+    if (options.modern !== false) {
+      const config = configs.find(i => i.name === 'modern')
+      if (config) {
+        fn(config)
+      }
+    }
   })
 }