Refactor to use the new custom modal builder

[candela97]

.

[tfedor]

Width of the form like this won't work. Width must be defined when the modal is created, otherwise the modal won't be centered.

[candela97]

It looks just the same to me before and after this pr 🤔

I think the resize event handles this.

[tfedor]

Looks like you're right, but it's weird because I remember it didn't work when I was implementing it - that's why I added that to the div directly. Not quite sure what's different now.