switch to vue cli for build

tests/unit/example.spec.js

@@ -0,0 +1,12 @@
+import { shallowMount } from "@vue/test-utils";
+import HelloWorld from "@/components/HelloWorld.vue";
+
+describe("HelloWorld.vue", () => {
+  it("renders props.msg when passed", () => {
+    const msg = "new message";
+    const wrapper = shallowMount(HelloWorld, {
+      props: { msg }
+    });
+    expect(wrapper.text()).toMatch(msg);
+  });
+});