refactor: update Button to always use a size, determine tag from url

apps/website/src/components/atoms/Button.svelte

@@ -6,22 +6,23 @@
     import { cx } from 'classix'
     import SplitText from '$components/SplitText.svelte'
 
-    export let tag = 'a'
     export let text: string
     export let url: string = undefined
     export let color: string = undefined
-    export let size: string = undefined
+    export let size: 'xsmall' | 'small' | 'medium' | 'large'
     export let effect = 'link-3d'
     export let disabled: boolean = undefined
     export let slotPosition = 'before'
 
-    const className = 'button'
+    let tag: 'a' | 'button'
+    $: tag = url ? 'a' : 'button'
+
     $: classes = cx(
-        className,
+        'button',
         effect ? effect : undefined,
-        ...[color, size].map(variant => variant && `${className}--${variant}`),
+        ...[color, size].map(variant => variant && `button--${variant}`),
         Object.keys($$slots).length !== 0 ? `has-icon-${slotPosition}` : undefined,
-        $$props.class
+        $$props.class,
     )
 
     // Define external links