Add missing class to button

Author: lnbc1QWFyb24

src/elements/Button.svelte

@@ -39,7 +39,7 @@
 
 <button
   on:click={onclick}
-  class="bn-onboard-prepare-button"
+  class="bn-onboard-custom bn-onboard-prepare-button"
   class:bn-onboard-prepare-button-right={position === 'right'}
   class:bn-onboard-prepare-button-left={position === 'left'}
   class:bn-onboard-prepare-button-center={position !== 'left' && position !== 'right'}