Add the insert field coffeescript
user
```coffeescript
class window.TheMerger 

  foobar: ->
    alert 'foo'

  insert_field: (body) ->
    alert body
  
  # start=$(".mail_merge_body").caret().start;
  # first_half=$(".mail_merge_body").val().slice(0, start);
  # last_half=$(".mail_merge_body").val().slice(start, $(".mail_merge_body").len);
  # text = first_half + "[" + $('#field').val() + "]" + last_half
  # $('.mail_merge_body').val(text)
  # false
```
assistant