Use custom mascot on static share page (#15687)

* Use custom mascot on static share page

* Use full_asset_url

app/helpers/mascot_helper.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module MascotHelper
+  def mascot_url
+    full_asset_url(instance_presenter.mascot&.file&.url || asset_pack_path('media/images/elephant_ui_plane.svg'))
+  end
+
+  private
+
+  def instance_presenter
+    @instance_presenter ||= InstancePresenter.new
+  end
+end