add test

packages/svelte/tests/css/samples/general-siblings-combinator-render-tag/expected.css

@@ -0,0 +1,4 @@
+
+	h1.svelte-xyz ~ p:where(.svelte-xyz) {
+		color: green;
+	}

packages/svelte/tests/css/samples/general-siblings-combinator-render-tag/input.svelte

@@ -0,0 +1,13 @@
+{#snippet foo()}
+	<p>this should be green</p>
+{/snippet}
+
+<h1>Hello</h1>
+
+{@render foo()}
+
+<style>
+	h1 ~ p {
+		color: green;
+	}
+</style>

packages/svelte/tests/css/samples/siblings-combinator-slot-named-between-default/Child.svelte

@@ -0,0 +1 @@
+<slot />

packages/svelte/tests/css/samples/siblings-combinator-slot-named-between-default/expected.css

@@ -0,0 +1,4 @@
+
+	.a.svelte-xyz + .c:where(.svelte-xyz) {
+		color: green;
+	}

packages/svelte/tests/css/samples/siblings-combinator-slot-named-between-default/input.svelte

@@ -0,0 +1,15 @@
+<script>
+	import Child from './Child.svelte';
+</script>
+
+<Child>
+	<div class="a">a</div>
+	<div class="b" slot="wut">b</div>
+	<div class="c">c</div>
+</Child>
+
+<style>
+	.a + .c {
+		color: green;
+	}
+</style>