tutorial: include example on how to use hoisted client functions

The [tutorial for Servant.Client](https://docs.servant.dev/en/stable/tutorial/Client.html) includes an example for using `hoidstClient` to move a client function into another monad.
But this example seems incomplete, as it only defines the `getClients` function without showing how to actually use it.
#1019 indicates that functions can be similarly pattern matched as already done with `client`. But then the problem arises how to pass in arguments like `clientEnv` in the tutorial.

So does the example from the tutorial make sense in the first place, and how shall it be used?