Correct fs.fsys usage

[catilac]

I saw that there were some changes to how fs.fsys is used. But I'm new to the codebase, and still exploring the project.

[Parzival-3141]

There's one last incorrect usage on line 304, but other than that looks good

@@ -301,7 +298,7 @@ func (s *Service) readdir(this js.Value, args []js.Value) any {
        go func() {                                                                
                log("readdir", path)                                               
                                                                                   
-               fi, err := fs.ReadDir(s.fsys, path)                                
+               fi, err := fs.ReadDir(s.fsys.FS, path)                             
                if err != nil {                                                    
                        cb.Invoke(jsutil.ToJSError(err))                           
                        return                                                     

[Parzival-3141]

Thank you!