Define when Button url is external

src/components/atoms/Button.svelte

@@ -16,6 +16,12 @@
         ...[color, size].map(variant => variant && `${className}--${variant}`),
         $$props.class
     ].join(' ').trim()
+
+    // Define external links
+    let rel: string, target: string
+    $: isExternal = /(http(s?)):\/\//i.test(url)
+    $: rel = isExternal ? 'external noopener noreferrer' : null
+    $: target = isExternal ? '_blank' : null
 </script>
 
 {#if tag === 'button'}
@@ -24,7 +30,13 @@
         <SplitText {text} clone={true} />
     </button>
 {:else if tag === 'a'}
-    <a href={url} class={classes} on:click sveltekit:prefetch>
+    <a
+        href={url} class={classes}
+        {rel} {target}
+        sveltekit:prefetch={url && isExternal ? null : true}
+        disabled={disabled}
+        on:click
+    >
         <slot />
         <SplitText {text} clone={true} />
     </a>