Run Piper ONNX in a module worker

tests/piper-worker-format.test.cjs

@@ -0,0 +1,13 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const {readFile} = require('node:fs/promises');
+const {join} = require('node:path');
+
+test('Piper worker is built and started as an ES module', async () => {
+  const [buildScript, runtime] = await Promise.all([
+    readFile(join(__dirname, '..', 'scripts', 'build-piper.mjs'), 'utf8'),
+    readFile(join(__dirname, '..', 'piper-runtime.js'), 'utf8'),
+  ]);
+  assert.match(buildScript, /outfile: join\(workerRoot, 'piper-worker\.js'\),\s*bundle: true,\s*format: 'esm'/);
+  assert.match(runtime, /new Worker\(workerUrl, \{type: 'module'\}\)/);
+});