Fix Translation Missing en.active_admin.create_model

On submitting a create / edit form for a resource where validations fail, the page rendered looks for create_model / update_model string. I've given a fix here for the en locales file, but have left the other languages as the fix could be made either in yml or in code (I'm not sure which is better overall, I've left the decision up to the maintainer).

Author: alzeih

lib/active_admin/locales/en.yml

@@ -9,7 +9,9 @@ en:
     delete: "Delete"
     delete_confirmation: "Are you sure you want to delete this?"
     new_model: "New %{model}"
+    create_model: "New %{model}"
     edit_model: "Edit %{model}"
+    update_model: "Edit %{model}"
     delete_model: "Delete %{model}"
     details: "%{model} Details"
     cancel: "Cancel"