Generate an ES module

package.json

@@ -1,7 +1,8 @@
 {
   "name": "web-serial-polyfill",
-  "version": "1.0.14",
+  "version": "1.0.15",
   "description": "An implementation of the [Serial API](https://wicg.github.io/serial) on top of the [WebUSB API](https://wicg.github.io/webusb) for use with USB-to-serial adapters. Use of this library is limited to hardware and platforms where the device is accessible via the WebUSB API because it has not been claimed by a built-in device driver. This project will be used to prototype the design of the Serial API.",
+  "type": "module",
   "main": "./dist/serial.js",
   "types": "./dist/serial.d.ts",
   "scripts": {

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "module": "commonjs",
+    "module": "es2015",
     "lib": ["es2017"],
     "outDir": "./dist/",
     "sourceMap": true,