Update manifest start URL and make drone auto-promote staging

.drone.yml

@@ -127,4 +127,19 @@ steps:
           "priority": 6
         }
     when:
-      status: failure
+      status: failure
+
+# ================ DEPLOY STAGING =====================
+  - name: promote staging build
+    image: plugins/downstream
+    settings:
+      server: https://ci.garrettmills.dev
+      token:
+        from_secret: drone_token
+      fork: false
+      last_successful: true
+      deploy: staging
+      repositories:
+        - Noded/frontent@master
+    when:
+      status: success

src/manifest.webmanifest

@@ -5,7 +5,7 @@
   "background_color": "#fafafa",
   "display": "standalone",
   "scope": "./i/",
-  "start_url": "./i/",
+  "start_url": "./i/index.html",
   "icons": [
     {
       "src": "assets/icons/icon-72x72.png",