LibJS: Add String.raw

Libraries/LibJS/Tests/String.raw.js

@@ -0,0 +1,35 @@
+load("test-common.js")
+
+try {
+    let str = String.raw`foo\nbar`;
+    assert(str.length === 8 && str === "foo\\nbar");
+
+    str = String.raw`foo ${1 + 9}\nbar${"hf!"}`;
+    assert(str === "foo 10\\nbarhf!");
+
+    str = String.raw`${10}${20}${30}`;
+    assert(str === "102030");
+
+    str = String.raw({ raw: ["foo ", "\\nbar"] }, 10, "hf!");
+    assert(str === "foo 10\\nbar");
+
+    str = String.raw({ raw: ["foo ", "\\nbar"] });
+    assert(str === "foo \\nbar");
+
+    str = String.raw({ raw: [] }, 10, "hf!");
+    assert(str === "");
+
+    str = String.raw({ raw: 1 });
+    assert(str === "");
+
+    assertThrowsError(() => {
+        String.raw({});
+    }, {
+        error: TypeError,
+        message: "Cannot convert property 'raw' to object from undefined",
+    });
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}