fix bug: upload-offset header should be string

Author: hoiekim

.changeset/happy-countries-ring.md

@@ -0,0 +1,5 @@
+---
+"@tus/server": minor
+---
+
+fix bug: upload-offset header should be string

packages/server/src/handlers/PatchHandler.ts

@@ -113,7 +113,7 @@ export class PatchHandler extends BaseHandler {
         status: 204,
         headers: {
           ...Object.fromEntries(headers.entries()),
-          'Upload-Offset': newOffset,
+          'Upload-Offset': newOffset.toString(),
         } as Record<string, string | number>,
         body: '',
       }