LibWeb: Implement '5.4. Request class' from the Fetch API :^)

Author: https://github.com/linusg
Commit: 9fb672e981
Pull-request: https://github.com/SerenityOS/serenity/pull/15359
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/davidot ✅
Reviewed-by: https://github.com/kennethmyhra

Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp

@@ -36,6 +36,8 @@ static bool is_platform_object(Type const& type)
         "Node"sv,
         "Path2D"sv,
         "Range"sv,
+        "ReadableStream"sv,
+        "Request"sv,
         "Selection"sv,
         "Text"sv,
         "TextMetrics"sv,
@@ -2097,7 +2099,9 @@ using namespace Web::IntersectionObserver;
 using namespace Web::RequestIdleCallback;
 using namespace Web::ResizeObserver;
 using namespace Web::Selection;
+using namespace Web::Streams;
 using namespace Web::UIEvents;
+using namespace Web::URL;
 using namespace Web::XHR;
 using namespace Web::WebGL;
 using namespace Web::WebIDL;
@@ -2410,6 +2414,7 @@ using namespace Web::NavigationTiming;
 using namespace Web::RequestIdleCallback;
 using namespace Web::ResizeObserver;
 using namespace Web::Selection;
+using namespace Web::Streams;
 using namespace Web::SVG;
 using namespace Web::UIEvents;
 using namespace Web::URL;