LibWeb: Serialize and pass to the WebWorker the current ESO

This allows the initial fetch() in the run a worker AO to use the proper
values from the outside settings.

Meta/gn/secondary/Userland/Libraries/LibWeb/HTML/Scripting/BUILD.gn

@@ -3,6 +3,7 @@ source_set("Scripting") {
   deps = [ "//Userland/Libraries/LibWeb:all_generated" ]
   sources = [
     "ClassicScript.cpp",
+    "EnvironmentSettingsSnapshot.cpp",
     "Environments.cpp",
     "ExceptionReporter.cpp",
     "Fetching.cpp",