LibDevTools: Implement enough of the protocol to inspect tabs

There is a lot needed all at once to actually inspect a tab's DOM tree.
It begins with requesting a "watcher" from a TabActor. It seems there
can be many types of watchers, but here we implement the "frame" watcher
only. The watcher creates an "inspector", which in turn creates a
"walker", which is the actor ultimately responsible for serializing and
inspecting the DOM tree.

In between all that, the DevTools client will send a handful of other
informational requests. If we do not reply to these, the client will not
move forward with the walker. For example, the CSSPropertiesActor will
be asked for a list of all known CSS properties.

Libraries/LibDevTools/Actors/TargetConfigurationActor.cpp

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/JsonArray.h>
+#include <AK/JsonObject.h>
+#include <LibDevTools/Actors/TargetConfigurationActor.h>
+
+namespace DevTools {
+
+NonnullRefPtr<TargetConfigurationActor> TargetConfigurationActor::create(DevToolsServer& devtools, ByteString name)
+{
+    return adopt_ref(*new TargetConfigurationActor(devtools, move(name)));
+}
+
+TargetConfigurationActor::TargetConfigurationActor(DevToolsServer& devtools, ByteString name)
+    : Actor(devtools, move(name))
+{
+}
+
+TargetConfigurationActor::~TargetConfigurationActor() = default;
+
+void TargetConfigurationActor::handle_message(StringView type, JsonObject const& message)
+{
+    JsonObject response;
+    response.set("from"sv, name());
+
+    if (type == "updateConfiguration"sv) {
+        auto configuration = message.get_object("configuration"sv);
+        if (!configuration.has_value()) {
+            send_missing_parameter_error("configuration"sv);
+            return;
+        }
+
+        send_message(move(response));
+        return;
+    }
+
+    send_unrecognized_packet_type_error(type);
+}
+
+JsonObject TargetConfigurationActor::serialize_configuration() const
+{
+    JsonObject supported_options;
+    supported_options.set("cacheDisabled"sv, false);
+    supported_options.set("colorSchemeSimulation"sv, false);
+    supported_options.set("customFormatters"sv, false);
+    supported_options.set("customUserAgent"sv, false);
+    supported_options.set("javascriptEnabled"sv, false);
+    supported_options.set("overrideDPPX"sv, false);
+    supported_options.set("printSimulationEnabled"sv, false);
+    supported_options.set("rdmPaneMaxTouchPoints"sv, false);
+    supported_options.set("rdmPaneOrientation"sv, false);
+    supported_options.set("recordAllocations"sv, false);
+    supported_options.set("reloadOnTouchSimulationToggle"sv, false);
+    supported_options.set("restoreFocus"sv, false);
+    supported_options.set("serviceWorkersTestingEnabled"sv, false);
+    supported_options.set("setTabOffline"sv, false);
+    supported_options.set("touchEventsOverride"sv, false);
+    supported_options.set("tracerOptions"sv, false);
+    supported_options.set("useSimpleHighlightersForReducedMotion"sv, false);
+
+    JsonObject traits;
+    traits.set("supportedOptions"sv, move(supported_options));
+
+    JsonObject target;
+    target.set("actor"sv, name());
+    target.set("configuration"sv, JsonObject {});
+    target.set("traits"sv, move(traits));
+
+    return target;
+}
+
+}