title: dialog.showModal not supported by Mozilla firefox any more
body: <p>I have a huge asp website project and for its popups, used from <code>showModalDialog</code>. Few months ago mozilla updated and some problem occured for this function. So I used <a href="https://github.com/niutech/showModalDialog" rel="nofollow noreferrer">ModalDialog polyfill</a> to solve. But in last mozilla update, <code>dialog.showModal()</code> function is out of support and none of my popups open. Although they gave such <a href="https://developer.mozilla.org/en-US/docs/Web/API/HTMLDialogElement/showModal" rel="nofollow noreferrer">solution</a> to enabled via the dom.dialog_element.enabled preference in about:config, but it disturbs users.</p>
  
  <p>I searched a lot about this but not find any solution to replace my codes. Because of hugeness of my project, it is so hard to use something such modal bootstrap. My popups and modals have some return values to save and such interactions. please introduce an alternative for this. Or help how can I write a new thing for this.</p>
  
  <p>thanks.</p>