Not disable alternate heading buttons

[inspire22]

Thanks for this great project! Seeing it is what made me finally dive into switching from ckeditor to trix, which I'd been wanting to do for awhile but some features were missing I'd promised people would be there.

I'm not a fan of how choosing one heading button disables the others until you toggle off the first one.

Any tips how to try changing this? I can't find any event listeners for x-heading, so it must be some internal trix thing based on dialogHeadingTemplate()?