LibWeb: Implement BufferSource support for XHR::send()

Author: https://github.com/kennethmyhra
Commit: 9a1c27a163
Pull-request: https://github.com/SerenityOS/serenity/pull/14648
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h

@@ -24,7 +24,7 @@
 namespace Web::XHR {
 
 // https://fetch.spec.whatwg.org/#typedefdef-xmlhttprequestbodyinit
-using XMLHttpRequestBodyInit = Variant<NonnullRefPtr<FileAPI::Blob>, NonnullRefPtr<URL::URLSearchParams>, String>;
+using XMLHttpRequestBodyInit = Variant<NonnullRefPtr<FileAPI::Blob>, JS::Handle<JS::Object>, NonnullRefPtr<URL::URLSearchParams>, String>;
 
 class XMLHttpRequest final
     : public RefCounted<XMLHttpRequest>