feat(effectScope): add `active` property getter

[webfansplz]

Close #6186

[LinusBorg]

The problem with this change is that now we communicate via our types that it's fine to mutate this property in userland - it's part of the types, after all. But that's not* what people should be doing.

So I think a better solution would be to have a dedicated getter for retrieving this information.

[webfansplz]

The problem with this change is that now we communicate via our types that it's fine to mutate this property in userland - it's part of the types, after all. But that's not* what people should be doing.

So I think a better solution would be to have a dedicated getter for retrieving this information.

Updated,Thanks for your suggestion.