Nanoservices event subscriber

A basic proc macro crate for subscribing to events. We can subscribe to events with the following code:

#[derive(Serialize, Deserialize, Debug)]
struct Two;

#[subscribe_to_event]
async fn test2(two: Two) {
    println!("calling from test2 function with: {:?}", two);
}

This generates the code for a standard function under the name as it is defined as, and a slightly mangled function which is registered with the event subscriber. If an event is then published with the Two then all functions subscribed to the Two event will be called with the instance of the Two struct.