Install chromium for prod + extend process timeout

app/controllers/contestants_controller.rb

@@ -131,6 +131,10 @@ class ContestantsController < ApplicationController
     @contestants = @contest.contestants.sort_by { |contestant| contestant.name }
     @nonav = true
 
+    FerrumPdf.configure do |config|
+      config.process_timeout = 20
+    end
+
     respond_to do |format|
       format.html
       format.pdf { render ferrum_pdf: {}, disposition: :inline, filename: "#{@contest.friendly_id}_qrcodes.pdf", layout: "blank" }