added TWA assetlinks and related apps

public/manifest.json

@@ -4,6 +4,7 @@
   "lang": "en-GB",
   "description": "Travel planning without the headaches! Let's Plan is a free, easy to use travel planner app that's smart and intuitive. It's designed to work offline and in rough data patches. It's open source and actively maintained, feel free to contribute!",
   "categories": ["travel", "utilities", "social"],
+  "iarc_rating_id": "e8e543f1-e8c9-4319-be7c-f17f71d29b8b",
   "icons": [
     {
       "src": "favicon.ico",
@@ -121,6 +122,18 @@
       "label": "You can add a wide range of activities and trips by default."
     }
   ],
+  "related_applications": [
+    {
+      "platform": "play",
+      "url": "https://play.google.com/store/apps/details?id=com.dylmye.letsplan",
+      "id": "com.dylmye.letsplan"
+    },
+    {
+      "platform": "windows",
+      "url": "https://www.microsoft.com/store/apps/9NSBKF403JDD"
+    }
+  ],
+  "prefer_related_applications": false,
   "shortcuts": [
     {
       "name": "List your trips",