add test

test/css/samples/global-with-unused-descendant/_config.js

@@ -0,0 +1,24 @@
+export default {
+	warnings: [{
+		code: 'css-unused-selector',
+		end: {
+			character: 27,
+			column: 19,
+			line: 2
+		},
+		frame: `
+			1: <style>
+			2:   :global(.foo) .bar {
+			     ^
+			3:     color: red;
+			4:   }
+		`,
+		message: 'Unused CSS selector',
+		pos: 9,
+		start: {
+			character: 9,
+			column: 1,
+			line: 2
+		}
+	}]
+};

test/css/samples/global-with-unused-descendant/input.svelte

@@ -0,0 +1,5 @@
+<style>
+	:global(.foo) .bar {
+		color: red;
+	}
+</style>