LibJS: Implement Temporal.PlainDate.prototype.dayOfYear

Author: https://github.com/IdanHo
Commit: d561535ac9
Pull-request: https://github.com/SerenityOS/serenity/pull/8961
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.dayOfYear.js

@@ -0,0 +1,14 @@
+describe("correct behavior", () => {
+    test("basic functionality", () => {
+        const date = new Temporal.PlainDate(2021, 7, 23);
+        expect(date.dayOfYear).toBe(204);
+    });
+});
+
+test("errors", () => {
+    test("this value must be a Temporal.PlainDate object", () => {
+        expect(() => {
+            Reflect.get(Temporal.PlainDate.prototype, "dayOfYear", "foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.PlainDate");
+    });
+});