Changes:
- [change][major] Add `hidden` field to items in interface introspection types.
- [add][minor] Add `#[hidden]` attribute for interfaces, services, streams and updates in `interface! { ... }` macro.
- [add][minor] Add documentation about the protocol itself.
- [add][minor] Add `same_peer` function to `PeerWriteHandle` to check if they belong to the same peer.
- [fix][patch] Fix clippy warnings for unnecessary casting.