Add modal width breakpoints as CSS Variables

[VMLuca]

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

Currently only width breakpoints are available as SCSS variables for the modal.

modal-sm: 300px;
$modal-md:                          500px;
$modal-lg:                          800px;
$modal-xl: 1140px;

Motivation and context

Please add the ability to add width breakpoints as CSS variables so that I can set different breakpoints for different modals and not just globally with sccs variables.

[poswalsameer]

Hii @VMLuca, can you please describe the issue more briefly, I went through the _variables.scss, these breakpoints are already available there.

[VMLuca]

_variables.scss is about scss variabels, isn't it? I was talking about CSS variables