Create the Shell trait

[sphinxc0re]

Create a trait which allows devs to implement their own I/O system around the actual VM while using the same instruction set

trait Shell {
    type Error;

    /// Is called right before the VM executes code
    fn prepare(&mut self, &mut VM) -> Result<(), Self::Error>;
    /// Sends the given buffer to the shell
    fn send_buffer(&mut self, &Buffer) -> Result<(), Self::Error>;
    /// Receives and handles an event
    fn receive_event(&mut self, &Event) -> Result<(), Self::Error>;
}