LibCore: Implement StandardPaths::user_data_directory on Windows

Author: https://github.com/stasoid
Commit: https://github.com/LadybirdBrowser/ladybird/commit/2e200489c83
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3002
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/AtkinsSJ

Libraries/LibCore/StandardPaths.cpp

@@ -157,8 +157,7 @@ ByteString StandardPaths::config_directory()
 ByteString StandardPaths::user_data_directory()
 {
 #ifdef AK_OS_WINDOWS
-    dbgln("Core::StandardPaths::user_data_directory() is not implemented");
-    VERIFY_NOT_REACHED();
+    return ByteString::formatted("{}/Ladybird"sv, getenv("LOCALAPPDATA"));
 #endif
     if (auto data_directory = get_environment_if_not_empty("XDG_DATA_HOME"sv); data_directory.has_value())
         return LexicalPath::canonicalized_path(*data_directory);