build: add esm bundle

Author: nieyuyao

packages/test-utils/package.json

@@ -3,6 +3,7 @@
   "version": "1.3.0",
   "description": "Utilities for testing Vue components.",
   "main": "dist/vue-test-utils.js",
+  "module": "dist/vue-test-utils.esm.js",
   "types": "types/index.d.ts",
   "files": [
     "dist/*.js",

packages/test-utils/scripts/build.js

@@ -31,6 +31,15 @@ const rollupOptionsBuild = [
       'vue-template-compiler': 'VueTemplateCompiler'
     }
   },
+  {
+    file: 'dist/vue-test-utils.esm.js',
+    format: 'esm',
+    name: 'VueTestUtils',
+    globals: {
+      vue: 'Vue',
+      'vue-template-compiler': 'VueTemplateCompiler'
+    }
+  },
   {
     file: 'dist/vue-test-utils.umd.js',
     format: 'umd',