fix: add maxDuration to PageConfig type (#55918)

Author: simonhaenisch

packages/next/types/index.d.ts

@@ -140,6 +140,11 @@ export type PageConfig = {
     externalResolver?: true
   }
   env?: Array<string>
+  /**
+   * Configures the longest time in seconds a serverless function can process an HTTP
+   * request before responding.
+   */
+  maxDuration?: number
   runtime?: ServerRuntime
   unstable_runtimeJS?: false
   unstable_JsPreload?: false