Number of Slides per Group Option needed

Here is a simple patch that adds the option to slidesPerGroup - might be worth adding slidesPerGroupAuto and hiding this option unless SlidesPerView is larger than 1 but as a simple way to add the option this seems to work.

Thanks! Finally I was able to grab some time to include this property too. It is enclosed in the new 2.0.x version, just released. Please also check out this issue about Breakpoints feature: https://www.drupal.org/project/swiper_formatter/issues/3441764 ✨ Breakpoints feature Needs review partially related.