add mixins

src/mixins/titleMixin.js

@@ -0,0 +1,16 @@
+function getTitle (vm) {
+  const { title } = vm.$options
+  if (title) {
+    return typeof title === 'function'
+      ? title.call(vm)
+      : title
+  }
+}
+export default {
+  created () {
+    const title = getTitle(this)
+    if (title) {
+      document.title = title
+    }
+  }
+}