Refactor/modal

[MartinWeb]

Related issue

Bug

Person(s) for reviewing proposed changes

@arnaudforaison @samuel-gomez @JLou @buddyvegas

Important

This pull request introduces breaking changes :

• the isOpen property has been removed to match the way of using the dialog element. We do not change visibility of the element anymore, we directly call the showModal or close functions to open and close the dialog
• related to that, i didn't find a way to continue the export of Modal.Header, Modal.Body, etc.... because of the usage of forwardRef. Instead i directly use Header, Body, etc... If someone has a way to make it work i am open to suggestion :)