title: Increase ignore_above property in elastic search
body: <p>I am using elastic search with nest 5.0</p>
  
  <p>I need to increase ignore_above from default 256 to 512.</p>
  
  <p>Can I do this by the Attribute mappings?</p>
  
  <p>Otherwise how can I do this using the fluent API?</p>