add test that should not be thrown

test/validator/samples/binding-this-invalid-foreign-namespace /errors.json

@@ -0,0 +1,15 @@
+[{
+	"code": "invalid-binding",
+	"message": "'this' is not a valid binding. Foreign elements only support bind:this",
+	"pos": 81,
+	"start": {
+		"line": 6,
+		"column": 7,
+		"character": 81
+	},
+	"end": {
+		"line": 6,
+		"column": 27,
+		"character": 101
+	}
+}]

test/validator/samples/binding-this-invalid-foreign-namespace /input.svelte

@@ -0,0 +1,6 @@
+<svelte:options namespace="foreign" />
+<script>
+	let whatever;
+</script>
+
+<input bind:this={whatever} />