fix(runtome-dom): properly support creating customized built-in element

packages/runtime-dom/__tests__/customizedBuiltIn.spec.ts

@@ -0,0 +1,20 @@
+import { render, h } from '@vue/runtime-dom'
+
+describe('customimized built-in elements support', () => {
+  let createElement: jest.SpyInstance
+  afterEach(() => {
+    createElement.mockRestore()
+  })
+
+  test('should created element with is option', () => {
+    const root = document.createElement('div')
+    createElement = jest.spyOn(document, 'createElement')
+    render(h('button', { is: 'plastic-button' }), root)
+    expect(createElement.mock.calls[0]).toMatchObject([
+      'button',
+      { is: 'plastic-button' }
+    ])
+    // should also render the attribute
+    expect(root.innerHTML).toBe(`<button is="plastic-button"></button>`)
+  })
+})