Add counter for abuse reports

app/views/layouts/nav/_admin.html.haml

@@ -72,6 +72,7 @@
     = link_to admin_abuse_reports_path, title: "Abuse Reports" do
       %span
         Abuse Reports
+        %span.badge.count= number_with_delimiter(AbuseReport.count(:all))
 
   - if askimet_enabled?
     = nav_link(controller: :spam_logs) do