[sql] Call from Rust side

I wanted to know if it's possible to make queries from the Rust side, or if should be using other library if I don't plan to use the frontend side.

Currently, with the store plugin I do this:

```
with_store(app.app_handle(), stores, path, |store| {
Ok(serde_json::from_value::(
store.get("credentials").unwrap().clone(),
)?)
})
.map_err(|_| "Error getting credentials".to_string())
```

I checked the code and it doesn't seem to be any method to call from the Rust side.