wip: make singleton mutations affect all app instances

packages/vue-compat/__tests__/globalConfig.spec.ts

@@ -1,5 +1,6 @@
 import Vue from '@vue/compat'
 import { toggleDeprecationWarning } from '../../runtime-core/src/compat/compatConfig'
+import { createApp } from '../src/esm-index'
 import { triggerEvent } from './utils'
 
 beforeEach(() => {
@@ -64,3 +65,12 @@ test('GLOBAL_IGNORED_ELEMENTS', () => {
   })
   expect(el.innerHTML).toBe(`<v-foo></v-foo><foo></foo>`)
 })
+
+test('singleton config should affect apps created with createApp()', () => {
+  Vue.config.ignoredElements = [/^v-/, 'foo']
+  const el = document.createElement('div')
+  createApp({
+    template: `<v-foo/><foo/>`
+  }).mount(el)
+  expect(el.innerHTML).toBe(`<v-foo></v-foo><foo></foo>`)
+})