fix(wizard): prevent footer from covering dropdown

The z-index was set to 20 to prevent the language indicator for code sample from showing, but this caused other things to be hidden.

Since the language tag has a z-index of 2, we can make the footer have a z-index of 5 so it covers the language tag, but doesn't cover a dropdown

src/lib/layout/wizard.svelte

@@ -187,7 +187,7 @@
                     <svelte:component this={component} />
                 {/if}
             {/each}
-            <div class="u-z-index-20 form-footer">
+            <div class="u-z-index-5 form-footer">
                 <div class="u-flex u-main-end u-gap-12">
                     {#if !isLastStep && currentStep?.optional}
                         <Button text on:click={() => dispatch('finish')}>