LibWeb: Support SRI for import maps

See:
- https://github.com/whatwg/html/commit/b2fdca1

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp

@@ -416,6 +416,10 @@ void HTMLScriptElement::prepare_script()
         }
         // -> "module"
         else if (m_script_type == ScriptType::Module) {
+            // If el does not have an integrity attribute, then set options's integrity metadata to the result of resolving a module integrity metadata with url and settings object.
+            if (!has_attribute(HTML::AttributeNames::integrity))
+                options.integrity_metadata = MUST(resolve_a_module_integrity_metadata(url, settings_object));
+
             // Fetch an external module script graph given url, settings object, options, and onComplete.
             fetch_external_module_script_graph(realm(), url, settings_object, options, on_complete);
         }