feat: update theme swiper (#2404)

* Update template and styles StackedCardsSwiper

* Update styles and add hover transitions

* Hide partly visible slides

* Firefox fix wrapper overflowing slides

* Tweak transitions

* Show description on keyup, touchend and pointerup events

* Keep hover effect on initial slide and make entire slide a link

* Clean up now redundant outline-overlay button style

* Use pointer-events instead of pseudo element

* Fix indentation

* Show initial slide content on non-hover devices

* Update unit tests

* Fix descending specificity

* chore: update swiper package (#2407)

* Update swiper to lastest v11.1.5; update and clean up swiper instances

* Enable the swiper A11y module

* Add translation strings for a11y labels

* Use ImageOptimised in StackedCardsSwiper

* disable pointer events on cards

* button hover styles for background-cards

* Handle slide click instead of relying on slideToClickedSlide

* Make slides visible when not overflowing container

* Fix active swiper slide class

* Fix visible slide at breakpoint 1666px

* Fix unit tests

* Set default transform scale to prevent FF image disappearing

* bump size limits

---------

Co-authored-by: lbiedinger <lutz.biedinger@gmail.com>

packages/portal/docs/style/BootstrapVue/Button.md

@@ -288,25 +288,3 @@ _Used in the 'add item to gallery' modal_
     </b-button>
   </b-container>
 ```
-
-Variant "outline-overlay"<br>
-_Used in the themes swiper_
-
-```jsx
-  <b-container class="d-flex flex-wrap">
-    <div class="mr-3 mb-3" :style="`{ margin: -16px; padding: 32px; background-color: #000; }`">
-      <b-button
-        variant="outline-overlay"
-      >
-        <span>Label no image</span>
-      </b-button>
-    </div>
-    <div class="mr-3 mb-3" :style="`{ margin: -16px; padding: 32px; background-image: url(${thumbnails[3]}); background-size: cover; }`">
-      <b-button
-        variant="outline-overlay"
-      >
-        <span>Label with image</span>
-      </b-button>
-    </div>
-  </b-container>
-```