LibWeb+WebDriver: Begin processing and matching WebDriver capabilities

Still some TODOs here:
* We don't handle all capabilities (e.g. proxy)
* We don't match the capabilities against the running browser

But this will parse the capabilities JSON object received from the
WebDriver client.

Userland/Libraries/LibWeb/WebDriver/Capabilities.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/StringView.h>
+#include <LibWeb/WebDriver/Response.h>
+
+namespace Web::WebDriver {
+
+// https://w3c.github.io/webdriver/#dfn-page-load-strategy
+enum class PageLoadStrategy {
+    None,
+    Eager,
+    Normal,
+};
+
+constexpr PageLoadStrategy page_load_strategy_from_string(StringView strategy)
+{
+    if (strategy == "none"sv)
+        return PageLoadStrategy::None;
+    if (strategy == "eager"sv)
+        return PageLoadStrategy::Eager;
+    if (strategy == "normal"sv)
+        return PageLoadStrategy::Normal;
+    VERIFY_NOT_REACHED();
+}
+
+// https://w3c.github.io/webdriver/#dfn-unhandled-prompt-behavior
+enum class UnhandledPromptBehavior {
+    Dismiss,
+    Accept,
+    DismissAndNotify,
+    AcceptAndNotify,
+    Ignore,
+};
+
+constexpr UnhandledPromptBehavior unhandled_prompt_behavior_from_string(StringView behavior)
+{
+    if (behavior == "dismiss"sv)
+        return UnhandledPromptBehavior::Dismiss;
+    if (behavior == "accept"sv)
+        return UnhandledPromptBehavior::Accept;
+    if (behavior == "dismiss and notify"sv)
+        return UnhandledPromptBehavior::DismissAndNotify;
+    if (behavior == "accept and notify"sv)
+        return UnhandledPromptBehavior::AcceptAndNotify;
+    if (behavior == "ignore"sv)
+        return UnhandledPromptBehavior::Ignore;
+    VERIFY_NOT_REACHED();
+}
+
+Response process_capabilities(JsonValue const& parameters);
+
+}