add note to install as an app

src/views/HomeView.vue

@@ -10,6 +10,21 @@
 
     <!-- show the actions for recognizing a give -->
     <div class="mb-8">
+      <div
+        v-if="!isInstalled()"
+        class="bg-amber-200 rounded-md overflow-hidden text-center px-4 py-3 mb-4"
+      >
+        <p>
+          You should install this as an app.
+          <router-link
+            :to="{ name: 'help-notifications' }"
+            class="text-blue-500"
+          >
+            Go here for instructions.
+          </router-link>
+        </p>
+      </div>
+
       <div
         v-if="!activeDid"
         class="bg-amber-200 rounded-md overflow-hidden text-center px-4 py-3 mb-4"
@@ -249,6 +264,18 @@ export default class HomeView extends Vue {
     }
   }
 
+  // from https://benborgers.com/posts/pwa-detect-installed
+  isInstalled() {
+    // For iOS
+    if ("standalone" in window.navigator) return true;
+
+    // For Android
+    if (window.matchMedia("(display-mode: standalone)").matches) return true;
+
+    // If neither is true, it's not installed
+    return false;
+  }
+
   public async buildHeaders() {
     const headers: HeadersInit = {
       "Content-Type": "application/json",