added hover effect to cta button

assets/sass/_theme/_configuration.sass

@@ -270,6 +270,8 @@ $block-call-to-action-background: $color-accent !default
 $block-call-to-action-color: $color-background !default
 $block-call-to-action-button-background: $color-background !default
 $block-call-to-action-button-color: $color-text !default
+$block-call-to-action-button-hover-background: $color-text-alt !default
+$block-call-to-action-button-hover-color: white !default
 
 // Block chapter
 $block-chapter-layout-accent-background: $color-accent !default

assets/sass/_theme/blocks/call_to_action.sass

@@ -30,6 +30,12 @@
                     @include btn
                     background: $block-call-to-action-button-background
                     color: $block-call-to-action-button-color
+                    transition: background .3s ease, color .3s ease
+                    &:hover,
+                    &:focus-visible,
+                    &:focus
+                        background: $block-call-to-action-button-hover-background
+                        color: $block-call-to-action-button-hover-color
                 &:last-child
                     margin-bottom: 0
         * + .actions