Intl.Collator: Add a test for search and sort in German.

Ref: https://github.com/tc39/ecma402/issues/256.

test/intl402/Collator/usage-de.js

@@ -0,0 +1,16 @@
+// Copyright 2018 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-initializecollator
+description: Checks the behavior of search and sort in German.
+includes: [compareArray.js]
+locale: [de]
+---*/
+
+assert.compareArray(["AE", "\u00C4"].sort(new Intl.Collator("de", {usage: "sort"}).compare),
+                    ["\u00C4", "AE"],
+                    "sort");
+assert.compareArray(["AE", "\u00C4"].sort(new Intl.Collator("de", {usage: "search"}).compare),
+                    ["AE", "\u00C4"],
+                    "search");