Better Add to Homescreen on Android

Adds standalone screen, and top-bar color and background color on splash screen

app/controllers/manifest_json_controller.rb

@@ -1,13 +1,15 @@
 class ManifestJsonController < ApplicationController
   layout false
-  skip_before_filter :preload_json, :check_xhr
+  skip_before_filter :preload_json, :check_xhr, :redirect_to_login_if_required
 
   def index
     manifest = {
       short_name: SiteSetting.title,
-      display: 'browser',
+      display: 'standalone',
       orientation: 'portrait',
-      start_url: "#{Discourse.base_uri}/"
+      start_url: "#{Discourse.base_uri}/",
+      background_color: "##{ColorScheme.hex_for_name('secondary')}",
+      theme_color: "##{ColorScheme.hex_for_name('header_background')}"
     }
 
     render json: manifest.to_json