✨ (header) back button if app installed

src/components/AppInstalled.vue

@@ -0,0 +1,21 @@
+<template>
+  <span>
+    <slot v-if="isInstalled" name="app-installed"></slot>
+    <slot v-else name="app-not-installed"></slot>
+  </span>
+</template>
+
+<script lang="ts">
+import { Component, Vue } from 'vue-property-decorator'
+
+@Component
+export default class AppInstalled extends Vue {
+  private isInstalled: boolean = false
+
+  private mounted() {
+    this.isInstalled =
+      window.matchMedia &&
+      window.matchMedia('(display-mode: standalone)').matches
+  }
+}
+</script>