Allow documentation at mock macro

[MOZGIII]

The code produced by the mock! macro cannot be documented right now, but we would like to expose our mocks to the public and provide the documentation for them.
Can you please add support for documentation?

[asomers]

Yeah, I can probably make this work. Could you please provide a short example of what you want to do?

[MOZGIII]

#![deny(missing_docs)]

// This code fails the missing docs check, simply put I want it to pass:

mock! {
    /// The mock for a `Trasport` interface. Use `MockTransport::new()` to create new mock.
    pub Transport {
        /// ...
        fn publish_request(
            &self,
            request: request::Publish,
        ) -> BoxFuture<'static, Result<Timetoken, MockTransportError>> {}

        /// ...
        fn subscribe_request(
            &self,
            request: request::Subscribe,
        ) -> BoxFuture<'static, Result<(Vec<Message>, Timetoken), MockTransportError>> {}
    }
    trait Clone {
        fn clone(&self) -> Self {}
    }
}

Just for clarity, in this example, the "main" trait is implemented separately (i.e. impl Transport for MockTransport { ... }).

[asomers]

@MOZGIII try the linked PR. Let me know if it fixes your problem.