this works:
```rust
#[doc=concat!("This defines the postcard-rpc app implementation for ", stringify!($app_name))]
```

found via: https://stackoverflow.com/a/78426606

should i do that? do you have a better text in mind which describes the app more accurately?
or should i just go for `#[doc(hidden)]`? (would that break consumers which for some reason already reference it in their docs if it suddenly doesn't show up anymore? i never thought about whether suddenly hiding something from the docs would be a breaking change?)