Setup Chapter in Book Has Unclear Event Struct

[DeanBDean]

Description

In chapter 7 of the book, under custom setup functionality, the tutorial instructs the user to create a struct Sys with a field reader that looks like ReaderId<Event>. cargo check gives the error cannot find type `Event` in this scope. If I try to import specs::shrev::Event, that doesn't really work since Event is a trait.

Meta

Rust version: 1.47.0
Specs version / commit: 0.16.1
Operating system: macOS 10.15.6

Reproduction

Steps to reproduce the behavior:

1. Go to setup
2. Go through the tutorial up to Custom Setup Functionality
3. Run cargo check after doing the first code snippet in Custom Setup Functionality

Expected behavior

The code returns no errors or warnings. I am willing to submit a PR over this issue, but I am unsure what Event should be