AK: Add a new, spec-compliant URLParser

This adds a new URL parser, which aims to be compliant with the URL
specification (https://url.spec.whatwg.org/). It also contains a
rudimentary data URL parser.

AK/URLParser.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2021, Max Wipfli <mail@maxwipfli.ch>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Optional.h>
+#include <AK/StringView.h>
+#include <AK/URL.h>
+
+namespace AK {
+
+class URLParser {
+public:
+    enum class State {
+        SchemeStart,
+        Scheme,
+        NoScheme,
+        SpecialRelativeOrAuthority,
+        PathOrAuthority,
+        Relative,
+        RelativeSlash,
+        SpecialAuthoritySlashes,
+        SpecialAuthorityIgnoreSlashes,
+        Authority,
+        Host,
+        Hostname,
+        Port,
+        File,
+        FileSlash,
+        FileHost,
+        PathStart,
+        Path,
+        CannotBeABaseUrlPath,
+        Query,
+        Fragment
+    };
+
+    static URL parse(Badge<URL>, const StringView& input, const URL* base_url = nullptr);
+
+private:
+    static Optional<URL> parse_data_url(const StringView& raw_input);
+};
+
+}
+
+using AK::URLParser;