fix: collapse header mobile

pages/contact-us.vue

@@ -0,0 +1,13 @@
+<template>
+  <div>
+    Contact
+  </div>
+</template>
+
+<script>
+import { Vue, Component } from 'nuxt-property-decorator'
+
+@Component
+export default class ContactUs extends Vue {
+}
+</script>