LibURL: Add representations of URLPattern{Init,Options,Input}

The URLPattern spec is intended to be implemented inside of LibURL, with
LibWeb only responsible for the IDL conversion layer, in a similar
manner to how URL is implemented.

Libraries/LibURL/Pattern/Init.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Optional.h>
+#include <AK/String.h>
+
+namespace URL::Pattern {
+
+// https://urlpattern.spec.whatwg.org/#dictdef-urlpatterninit
+struct Init {
+    Optional<String> protocol;
+    Optional<String> username;
+    Optional<String> password;
+    Optional<String> hostname;
+    Optional<String> port;
+    Optional<String> pathname;
+    Optional<String> search;
+    Optional<String> hash;
+    Optional<String> base_url;
+};
+
+}

Libraries/LibURL/Pattern/Pattern.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Variant.h>
+#include <LibURL/Pattern/Init.h>
+
+namespace URL::Pattern {
+
+// https://urlpattern.spec.whatwg.org/#typedefdef-urlpatterninput
+using Input = Variant<String, Init>;
+
+// https://urlpattern.spec.whatwg.org/#dictdef-urlpatternoptions
+struct Options {
+    bool ignore_case { false };
+};
+
+}