LibJS: Start implementing Temporal.ZonedDateTime

This commit adds the ZonedDateTime object itself, its constructor and
prototype (currently empty), and the CreateTemporalZonedDateTime
abstract operation.

Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.js

@@ -0,0 +1,39 @@
+describe("errors", () => {
+    test("called without new", () => {
+        expect(() => {
+            Temporal.ZonedDateTime();
+        }).toThrowWithMessage(
+            TypeError,
+            "Temporal.ZonedDateTime constructor must be called with 'new'"
+        );
+    });
+
+    test("out-of-range epoch nanoseconds value", () => {
+        expect(() => {
+            new Temporal.ZonedDateTime(8_640_000_000_000_000_000_001n);
+        }).toThrowWithMessage(
+            RangeError,
+            "Invalid epoch nanoseconds value, must be in range -86400 * 10^17 to 86400 * 10^17"
+        );
+        expect(() => {
+            new Temporal.ZonedDateTime(-8_640_000_000_000_000_000_001n);
+        }).toThrowWithMessage(
+            RangeError,
+            "Invalid epoch nanoseconds value, must be in range -86400 * 10^17 to 86400 * 10^17"
+        );
+    });
+});
+
+describe("normal behavior", () => {
+    test("length is 2", () => {
+        expect(Temporal.ZonedDateTime).toHaveLength(2);
+    });
+
+    test("basic functionality", () => {
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = new Temporal.ZonedDateTime(0n, timeZone);
+        expect(typeof zonedDateTime).toBe("object");
+        expect(zonedDateTime).toBeInstanceOf(Temporal.ZonedDateTime);
+        expect(Object.getPrototypeOf(zonedDateTime)).toBe(Temporal.ZonedDateTime.prototype);
+    });
+});