add distDir to nextjs config type

Author: lobsterkatie

packages/nextjs/src/config/types.ts

@@ -15,6 +15,8 @@ export type NextConfigObject = {
   webpack: WebpackConfigFunction;
   // whether to build serverless functions for all pages, not just API routes
   target: 'server' | 'experimental-serverless-trace';
+  // the output directory for the built app (defaults to ".next")
+  distDir: string;
   sentry?: {
     disableServerWebpackPlugin?: boolean;
     disableClientWebpackPlugin?: boolean;