chore: Add demo file with tabs

To showcase the GitHub web UI using URL state to set tab width.

Author: franky47

.prettierignore

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+demo-tabs.tsx

demo-tabs.tsx

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+'use client'
+
+import { parseAsInteger, useQueryState } from 'nuqs'
+
+export function Demo() {
+	const [hello, setHello] = useQueryState('hello', { defaultValue: '' })
+	const [count, setCount] = useQueryState(
+		'count',
+		parseAsInteger.withDefault(0)
+	)
+	return (
+		<>
+			<button
+				className="peer inline-flex h-10 items-center justify-center whitespace-nowrap rounded-md bg-primary px-4 py-2 text-sm font-medium tabular-nums text-primary-foreground ring-offset-background transition-colors hover:bg-primary/90 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50"
+				onClick={() => setCount(c => c + 1)}
+				data-interacted={count > 0}
+			>
+				Count: {count}
+			</button>
+			<input
+				value={hello}
+				placeholder="Enter your name"
+				className="peer flex h-10 rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background file:border-0 file:bg-transparent file:text-sm file:font-medium placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50"
+				onChange={e => setHello(e.target.value || null)}
+				data-interacted={Boolean(hello)}
+			/>
+			<p>Hello, {hello || 'anonymous visitor'}!</p>
+		</>
+	)
+}