migrate to "export default"

also, set no-use-before-define in linter

src/backupformat/tgz.js

@@ -1,9 +1,10 @@
 import assert from 'node:assert';
-import * as backupSites from '../backupsites.js';
+import backupSites from '../backupsites.js';
 import BoxError from '../boxerror.js';
 import DataLayout from '../datalayout.js';
 import debugModule from 'debug';
-import { DecryptStream, EncryptStream } from '../hush.js';
+import hush from '../hush.js';
+const { DecryptStream, EncryptStream } = hush;
 import fs from 'node:fs';
 import HashStream from '../hash-stream.js';
 import path from 'node:path';
@@ -347,7 +348,7 @@ function getFileExtension(encryption) {
 
 const _EnsureFileSizeStream = EnsureFileSizeStream;
 
-export {
+export default {
     download,
     upload,
     verify,