[BUG] Web App Manifest origin incorrect, icon images reference wrong path

[justinribeiro]

Description:

Currently the web app manifest definition located at public/images/manifest.json contains two errors as reported by Google Chrome DevTools:

1. Manifest: property 'start_url' ignored, should be same origin as document.
2. Icon downloaded from the manifest was empty or corrupted

Expected behavior:

The manifest should allow the application to be added to the home screen on Android or other platforms that support the Web App Manifest API specification.

Actual behavior:

1. Google Chrome for Android will install the incorrect icon on the homescreen.
2. Mozilla Firefox for Android will not properly prompt for homescreen addition.

Relevant logs:

[christianprim]

manifest.json should look like this:
{ "name": "Rocket.Chat", "icons": [ { "src": "\/assets\/favicon_192.png", "sizes": "192x192", "type": "image\/png" }, { "src": "\/assets\/favicon_512.png", "sizes": "512x512", "type": "image\/png" } ], "start_url": "\/home", "display": "standalone" }
icon-src must be absolute. start_url relative.