LibJS: Add the DataView built-in object

Userland/Libraries/LibJS/Tests/builtins/DataView/DataView.js

@@ -0,0 +1,15 @@
+test("basic functionality", () => {
+    expect(DataView).toHaveLength(1);
+    expect(DataView.name).toBe("DataView");
+    expect(DataView.prototype.constructor).toBe(DataView);
+
+    const buffer = new ArrayBuffer();
+    expect(new DataView(buffer)).toBeInstanceOf(DataView);
+    expect(typeof new DataView(buffer)).toBe("object");
+});
+
+test("DataView constructor must be invoked with 'new'", () => {
+    expect(() => {
+        DataView();
+    }).toThrowWithMessage(TypeError, "DataView constructor must be called with 'new'");
+});