chore: add css regression test (#11658)

closes #9207

packages/svelte/tests/css/samples/global-with-data-attribute/expected.css

@@ -0,0 +1,3 @@
+	.foo.svelte-xyz[data-state='checked'] {
+		background-color: red;
+	}

packages/svelte/tests/css/samples/global-with-data-attribute/input.svelte

@@ -0,0 +1,7 @@
+<!-- an action or sth else could dynamically set the data-state -->
+<div class="foo"></div>
+<style>
+	.foo:global([data-state='checked']) {
+		background-color: red;
+	}
+</style>