LibWeb: Set Cookie header on <img> and <object> resource requests

This required passing a reference to the owning HTML*Element to
ImageLoader, the same way that CSSLoader has a reference to its owner.

Userland/Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -38,6 +38,7 @@ namespace Web::HTML {
 
 HTMLImageElement::HTMLImageElement(DOM::Document& document, QualifiedName qualified_name)
     : HTMLElement(document, move(qualified_name))
+    , m_image_loader(*this)
 {
     m_image_loader.on_load = [this] {
         this->document().update_layout();