LibWeb: Add HTML::POSTResource

This is "POST resource" from the HTML spec.

Userland/Libraries/LibWeb/Forward.h

@@ -407,6 +407,7 @@ struct CrossOriginOpenerPolicyEnforcementResult;
 struct Environment;
 struct EnvironmentSettingsObject;
 struct NavigationParams;
+struct POSTResource;
 struct PolicyContainer;
 struct SandboxingFlagSet;
 struct SerializedFormData;

Userland/Libraries/LibWeb/HTML/POSTResource.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/browsing-the-web.html#post-resource
+struct POSTResource {
+    // FIXME: https://html.spec.whatwg.org/multipage/browsing-the-web.html#post-resource-request-body
+
+    enum class RequestContentType {
+        ApplicationXWWWFormUrlencoded,
+        MultipartFormData,
+        TextPlain,
+    };
+
+    // https://html.spec.whatwg.org/multipage/browsing-the-web.html#post-resource-request-content-type
+    // A request content-type, which is `application/x-www-form-urlencoded`, `multipart/form-data`, or `text/plain`.
+    RequestContentType request_content_type {};
+};
+
+}