chore: fix svelte check warning for tailwind css code

If there's no language specified for the style tag, the compiler thinks it's vanilla css and will output a warning. When adding `lang="postcss"` the compiler knows that we use tailwind directives and won't output that warning.

src/lib/components/composites/user-avatar/UserAvatar.svelte

@@ -59,7 +59,7 @@ Usage:
     {/if}
 </div>
 
-<style>
+<style lang="postcss">
     .review-decision {
         @apply absolute top-6 left-6 h-5 w-5 flex justify-center items-center rounded-full;
     }