Caching & worker queue components

Once #4 is settled and calls to `sudo` functions are possible the caching components could be added:

[https://staticbackend.com/docs/cache/](https://staticbackend.com/docs/cache/)

The worker queue has no documentation at time of writing, but it's implemented in [the Go library](https://github.com/staticbackendhq/backend-go/blob/main/cache.go#L37)