feat(*): Add stripe checkout support

src/routes/checkout/+page.svelte

@@ -0,0 +1,14 @@
+<script src="https://js.stripe.com/v3/"></script>
+
+<section>
+	<div class="product">
+		<img src="https://i.imgur.com/EHyR2nP.png" alt="The cover of Stubborn Attachments" />
+		<div class="description">
+			<h3>Stubborn Attachments</h3>
+			<h5>$20.00</h5>
+		</div>
+	</div>
+	<form action="/api/checkout" method="POST">
+		<button type="submit" id="checkout-button">Checkout</button>
+	</form>
+</section>