BREAKING CHANGE(core): switch to esm

test/test.ts

@@ -1,13 +1,13 @@
-import fs = require('fs');
+import fs from 'fs';
 import { expect, tap } from '@pushrocks/tapbundle';
 
-import * as smartstream from '../ts/index';
+import * as smartstream from '../ts/index.js';
 
 let testSmartstream: smartstream.Smartstream;
 tap.test('should combine a stream', async () => {
   testSmartstream = new smartstream.Smartstream([
     fs.createReadStream('./test/assets/test.md'),
-    fs.createWriteStream('./test/assets/testCopy.md')
+    fs.createWriteStream('./test/assets/testCopy.md'),
   ]);
   await testSmartstream.run();
 });