feat(toast): new centered variant to display in the middle of the screen

This PR adds a new centered variant to the toast position to be able to display them in the middle of the screen

$('body').toast({
  message: 'I am so centered',
  position: 'centered'
})

Author: lubber-de

src/definitions/modules/toast.less

@@ -103,6 +103,11 @@
       bottom: @toastContainerDistance;
     }
   }
+  &.centered when (@variationToastCentered) {
+    transform: translate(-50%, -50%);
+    top: 50%;
+    left: 50%;
+  }
   & .visible.toast-box,
   .animating.toast-box,
   .toast-box {

src/themes/default/globals/variation.variables

@@ -538,6 +538,7 @@
 @variationToastLeft: true;
 @variationToastRight: true;
 @variationToastCenter: true;
+@variationToastCentered: true;
 @variationToastInfo: true;
 @variationToastWarning: true;
 @variationToastSuccess: true;