Allow multiple submits of form[method="dialog"]

Problem/Motivation

Drupal has build in protection of submitting forms twice.
This applies to ''submit.singleSubmit'' and "form:not([method~="GET"])".
The second means all forms which are not method GET. This would include get (because case insensitive i not used) post, dialog and a form without a method (defaults to GET).

This feature prevents you from closing dialogs twice.

Steps to reproduce

<dialog>
<form method="dialog">
  <button>close</button/>
</form>
</dialog>

Proposed resolution

'form:not([method~="GET" i]):not([method~="dialog" i])'

allow submitting dialog twice
also check for method="get"