LibWeb: Implement most of Service Worker registration

This approach will need some rework to be properly handled at the user
agent level instead of per renderer process, but it's a start.

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -635,6 +635,8 @@ set(SOURCES
     ResizeObserver/ResizeObserverSize.cpp
     SecureContexts/AbstractOperations.cpp
     ServiceWorker/Job.cpp
+    ServiceWorker/Registration.cpp
+    ServiceWorker/ServiceWorker.cpp
     SRI/SRI.cpp
     StorageAPI/NavigatorStorage.cpp
     StorageAPI/StorageKey.cpp