LibDevTools: Introduce a Firefox DevTools server library

To aid with debugging web page issues in Ladybird without needing to
implement a fully fledged inspector, we can implement the Firefox
DevTools protocol and use their DevTools. The protocol is described
here:

https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html

This commit contains just enough to connect to Ladybird from a DevTools
client.

Libraries/LibDevTools/DevToolsServer.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <AK/HashMap.h>
+#include <AK/NonnullOwnPtr.h>
+#include <AK/NonnullRefPtr.h>
+#include <LibCore/Socket.h>
+#include <LibDevTools/Actors/RootActor.h>
+#include <LibDevTools/Forward.h>
+
+namespace DevTools {
+
+using ActorRegistry = HashMap<ByteString, NonnullRefPtr<Actor>>;
+
+class DevToolsServer {
+public:
+    static ErrorOr<NonnullOwnPtr<DevToolsServer>> create(DevToolsDelegate&, u16 port);
+    ~DevToolsServer();
+
+    RefPtr<Connection>& connection() { return m_connection; }
+    DevToolsDelegate const& delegate() const { return m_delegate; }
+    ActorRegistry const& actor_registry() const { return m_actor_registry; }
+
+    template<typename ActorType, typename... Args>
+    ActorType& register_actor(Args&&... args)
+    {
+        ByteString name;
+
+        if constexpr (IsSame<ActorType, RootActor>) {
+            name = ActorType::base_name;
+        } else {
+            name = ByteString::formatted("server{}-{}{}", m_server_id, ActorType::base_name, m_actor_count);
+        }
+
+        auto actor = ActorType::create(*this, name, forward<Args>(args)...);
+        m_actor_registry.set(name, actor);
+        ++m_actor_count;
+
+        return actor;
+    }
+
+private:
+    explicit DevToolsServer(DevToolsDelegate&, NonnullRefPtr<Core::TCPServer>);
+
+    ErrorOr<void> on_new_client();
+    void on_message_received(JsonObject const&);
+
+    void close_connection();
+
+    NonnullRefPtr<Core::TCPServer> m_server;
+    RefPtr<Connection> m_connection;
+
+    DevToolsDelegate& m_delegate;
+
+    ActorRegistry m_actor_registry;
+    RefPtr<RootActor> m_root_actor { nullptr };
+
+    u64 m_server_id { 0 };
+    u64 m_actor_count { 0 };
+};
+
+}