added healthcheck

app/controllers/healthcheck_controller.rb

@@ -0,0 +1,9 @@
+class ManifestController < ApplicationController
+  unloadable
+
+  skip_before_action :check_if_login_required
+
+  def index
+    render :layout => false, :action => 'index'
+  end
+end

app/views/healthcheck/index.html.erb

@@ -0,0 +1 @@
+OK