LibJS: Add tests for new Obj with optional chain

Author: https://github.com/ammarbinfaisal
Commit: c9088fa6ec
Pull-request: https://github.com/SerenityOS/serenity/pull/18813
Issue: https://github.com/SerenityOS/serenity/issues/18155
Reviewed-by: https://github.com/drunderscore

Userland/Libraries/LibJS/Tests/syntax/new-with-optional-chaining.js

@@ -0,0 +1,5 @@
+describe("parsing new expressions with optional chaining", () => {
+    expect("new Object()?.foo").toEval();
+    expect("new Object?.foo").not.toEval();
+    expect("(new Object)?.foo").toEval();
+});