support next.config.ts (#472)

* add next.config.ts check

* Create shy-readers-tease.md

---------

Co-authored-by: conico974 <nicodorseuil@yahoo.fr>

Author: aryasaatvik

.changeset/shy-readers-tease.md

@@ -0,0 +1,5 @@
+---
+"open-next": patch
+---
+
+support next.config.ts

packages/open-next/src/build.ts

@@ -129,7 +129,7 @@ function initTempDir() {
 
 function checkRunningInsideNextjsApp() {
   const { appPath } = options;
-  const extension = ["js", "cjs", "mjs"].find((ext) =>
+  const extension = ["js", "cjs", "mjs", "ts"].find((ext) =>
     fs.existsSync(path.join(appPath, `next.config.${ext}`)),
   );
   if (!extension) {