Use SMAppService to register the app to LoginItems instead of an AppleScript

At [Hopp](https://gethopp.app/), we want our app to start automatically on user login. Initially, we used the `autostart` plugin, which does the job but we thought that user experience can be improved.

In particular we found the two notifications the user receives slightly annoying.



We didn't like them because
* They are two instead of just one when using a native API.
* It isn’t entirely clear from the pop-ups which app is being added to the login items.

To address these, I decided to make [smappservice-rs](https://crates.io/crates/smappservice-rs), which is just a rust wrapper for macOS's `ServiceManagement` framework. When it is used instead of `auto-launch` it gives only one notification.

Would you consider accepting an enhancement to the `autostart` plugin that introduces a third option leveraging `smappservice-rs`?

I can also try extending `auto-launch` If you think that this change is more appropriate there. The reason I am first trying here is that `auto-launch` can be used to launch any app on start up, while `smappservice-rs` is for the running app only.

**Note:** I tested whether issue #2342 could be resolved using `smappservice-rs`, and it appears to work. Perhaps someone else could verify this as well.