Make Chrome splash screen same color as web UI's background color (#5169)

app/serializers/manifest_serializer.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class ManifestSerializer < ActiveModel::Serializer
+  include RoutingHelper
+  include ActionView::Helpers::TextHelper
+
+  attributes :name, :short_name, :description,
+             :icons, :theme_color, :background_color,
+             :display, :start_url, :scope
+
+  def name
+    object.site_title
+  end
+
+  def short_name
+    object.site_title
+  end
+
+  def description
+    strip_tags(object.site_description.presence || I18n.t('about.about_mastodon_html'))
+  end
+
+  def icons
+    [
+      {
+        src: '/android-chrome-192x192.png',
+        sizes: '192x192',
+        type: 'image/png',
+      },
+    ]
+  end
+
+  def theme_color
+    '#282c37'
+  end
+
+  def background_color
+    '#191b22'
+  end
+
+  def display
+    'standalone'
+  end
+
+  def start_url
+    '/web/timelines/home'
+  end
+
+  def scope
+    root_url
+  end
+end