Add Attachment Field in SharePoint 2013 List Form

Requirement: Add attachment column to a custom new/edit forms in SharePoint 2013.

Solution:
Create new custom list forms for New and Edit in SharePoint designer 2013, Add this code to the custom list form in the location where you want the attachment field to appear.

  
<td colspan="2">
 <table>
 <tr>
  <td style="width:170px">
       <b>Upload Approval E-Mails:    </b>
  </td>
  <td valign="top" class="ms-formbody" id="attachmentsOnClient">
   <input type="file" name="fileupload0"  id="onetidIOFile" size="50" title="Name">   </input>
  </td>
  <td>
   <input name="attachButton" type="button" value="Attach" onclick='OkAttach()'  />
  </td>  
 </tr>
      </table>
</td>    

Result: Here is the SharePoint custom edit form with attachment field.