fix: normalize component boundary spacing

packages/ui/components/BackToTop.wrn

@@ -1,5 +1,6 @@
 component BackToTop {
     props {
+        class = ""
         label = "Back to top"
         assistiveLabel = "Return to the top of the page"
         threshold = 500
@@ -49,7 +50,7 @@ component BackToTop {
 
     view {
         <div
-            class="group fixed bottom-6 right-5 z-[70] flex items-center gap-2 transition-all duration-300 sm:right-6 lg:bottom-8 lg:right-8"
+            class="group fixed bottom-6 right-5 z-[70] flex items-center gap-2 transition-all duration-300 sm:right-6 lg:bottom-8 lg:right-8 {class}"
             class:pointer-events-none="!visible"
             class:translate-y-5="!visible"
             class:scale-90="!visible"