fix buttons missing type="button"

Triggers unintentional form submits if missing `type` property.

src/lib/Tabs.svelte

@@ -93,6 +93,7 @@
 		{#each pages as page, i (page.title)}
 			{@const active = activeIndex === i}
 			<button
+				type="button"
 				bind:this={refs[i]}
 				class={['-mb-[2px] cursor-pointer px-2']}
 				onclick={() => {