Modal improvements

[kjugi]

Few updates to modal, I've worked with it in other project and have some issues to repair.
First in modal.hbs:

• importing trigger change to

{{#if trigger }}
    {{ render (component trigger) modalTrigger }}
{{/if}}

This will allow us to render trigger or variant of the trigger.

Second in _modal.scss:
Move overflow: auto; to .modal__content b/c if we have more than 100% height of content in modal it's cuts top of the modal content.

In modal-trigger.hbs:

{{ render '@button' buttonModalTrigger }} 

This will allow to add some i.e. variants of button.

[kjugi]

In addition to this we can change data naming to use kebab case in attributes.

Right now we have this on develop data-modaltrigger
And better will be when we will change it to this data-modal-trigger