Add entering transition on Shop and fix some styling

- Center intro title vertically
- Cart item styling tweaks
- Add cart button quantity label inside of button so it's clickable

src/components/organisms/Cart.svelte

@@ -140,7 +140,7 @@
         <div class="cart__content">
             {#if $cartAmount > 0}
                 {#each $cartData.items as item, index}
-                    <CartItem {item} {index}
+                    <CartItem {item}
                         on:updatedQuantity={changedQuantity}
                         on:removed={removedItem}
                     />
@@ -155,7 +155,7 @@
             {/if}
 
             {#if !$cartData || $cartIsUpdating}
-                <div class="cart__update">
+                <div class="cart__update" transition:fade={{ duration: 400 }}>
                     <p>Updating…</p>
                 </div>
             {/if}