LibWeb: Add initial implementation for WorkerGlobalScope

This initial implementation stubs out the WorkerGlobalScope,
WorkerLocation and WorkerNavigator classes. It doesn't take into account
all the things that actually need passed into the constructors for these
objects, nor the extra abstract operations that need to be performed on
them by the rest of the Browser infrastructure. However, it does create
bindings that compile and link :^)

Userland/Libraries/LibWeb/Forward.h

@@ -218,6 +218,9 @@ class SubmitEvent;
 class TextMetrics;
 class WebSocket;
 class WindowEnvironmentSettingsObject;
+class WorkerGlobalScope;
+class WorkerLocation;
+class WorkerNavigator;
 }
 
 namespace Web::HighResolutionTime {
@@ -465,6 +468,9 @@ class URLSearchParamsWrapper;
 class URLWrapper;
 class WebSocketWrapper;
 class WindowObject;
+class WorkerGlobalScopeWrapper;
+class WorkerLocationWrapper;
+class WorkerNavigatorWrapper;
 class Wrappable;
 class Wrapper;
 class XMLHttpRequestConstructor;