LibJS: Implement Temporal.PlainDateTime.prototype.equals()

Author: https://github.com/IdanHo
Commit: 32fc81c186
Pull-request: https://github.com/SerenityOS/serenity/pull/9636
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.equals.js

@@ -0,0 +1,13 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainDateTime.prototype.equals).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const calendar = { hello: "friends" };
+        const firstPlainDateTime = new Temporal.PlainDateTime(1, 1, 1, 1, 1, 1, 1, 1, 1, calendar);
+        const secondPlainDateTime = new Temporal.PlainDateTime(0, 1, 1, 1, 1, 1, 1, 1, 1, calendar);
+        expect(firstPlainDateTime.equals(firstPlainDateTime));
+        expect(!firstPlainDateTime.equals(secondPlainDateTime));
+    });
+});