manifest updates: remove deprecated density values; fix paths to ic…

…ons; update `background_color`; add `<meta name="theme-color">` tag

manifest.webmanifest

@@ -5,46 +5,43 @@
   "short_name": "A-Painter",
   "description": "Paint in VR in your browser. Powered by A-Frame.",
   "start_url": "./?src=manifest",
+  "scope": "./",
   "display": "fullscreen",
   "theme_color": "#0a0a0a",
-  "background_color": "#0a0a0a",
+  "background_color": "#030404",
   "icons": [
     {
-      "src": "/img/icon-512.png",
+      "src": "img/icon-512.png",
       "sizes": "512x512",
-      "type": "image/png",
-      "density": "2"
+      "type": "image/png"
     },
     {
-      "src": "/img/icon-256.png",
+      "src": "img/icon-256.png",
       "sizes": "256x256",
-      "type": "image/png",
-      "density": "2"
+      "type": "image/png"
     },
     {
-      "src": "/img/icon-128.png",
+      "src": "img/icon-128.png",
       "sizes": "128x128",
-      "type": "image/png",
-      "density": "2"
+      "type": "image/png"
     },
     {
-      "src": "/img/icon-64.png",
+      "src": "img/icon-64.png",
       "sizes": "64x64",
-      "type": "image/png",
-      "density": "2"
+      "type": "image/png"
     },
     {
-      "src": "/img/icon-32.png",
+      "src": "img/icon-32.png",
       "sizes": "32x32",
-      "type": "image/png",
-      "density": "2"
+      "type": "image/png"
     },
     {
-      "src": "/favicon.ico",
+      "src": "favicon.ico",
       "sizes": "16x16 32x32 48x48 64x64 256x256 512x512",
       "type": "image/x-icon"
     }
   ],
+  "about_url": "https://blog.mozvr.com/a-painter/",
   "vr_display_required": false,
   "vr_default_display": "HTC Vive",
   "vr_available_displays": [