Add section on using hooks

As a package dev, I'd like to have a reference section of hooks that are commonly used in packages and how to use them.

In particular, for my use case, I've been looking for a good reference implementation of using the `after-change-hooks` for building up a set of changes a user has made to the buffer.

IE:
If a user replaces a region of text
```
abcd => efgh
```
would look something like:
```
(:before-change "abcd"
:after-change "efgh")
```

or if a user deletes a char:
```
hello world => helloworld
```
would look like
```
(:before-change " "
:after-change "")
```
I've tried implementing this myself using the after-change-hook, but I keep running edges in my knowledge causing weird bugs.