LibJS: Begin implementing console.dir

The intent of the spec is that the output of console.dir is interactable
within the console. Our Printer implementation currently just prints the
provided object as a string, and doesn't check the provided `options`
argument. But having console.dir defined prevents exceptions from being
thrown on real websites.

Userland/Libraries/LibJS/Console.cpp

@@ -168,6 +168,26 @@ ThrowCompletionOr<Value> Console::warn()
     return js_undefined();
 }
 
+// 1.1.10. dir(item, options), https://console.spec.whatwg.org/#dir
+ThrowCompletionOr<Value> Console::dir()
+{
+    auto& vm = realm().vm();
+
+    // 1. Let object be item with generic JavaScript object formatting applied.
+    // NOTE: Generic formatting is performed by ConsoleClient::printer().
+    auto object = vm.argument(0);
+
+    // 2. Perform Printer("dir", « object », options).
+    if (m_client) {
+        MarkedVector<Value> printer_arguments { vm.heap() };
+        TRY_OR_THROW_OOM(vm, printer_arguments.try_append(object));
+
+        return m_client->printer(LogLevel::Dir, move(printer_arguments));
+    }
+
+    return js_undefined();
+}
+
 static ThrowCompletionOr<String> label_or_fallback(VM& vm, StringView fallback)
 {
     return vm.argument_count() > 0