I started doing this recently. Instead of using Github issues to track my todos, I just put everything in my README.md. Saves time and I don't have to go hunting for my notes. When titled, "Project Requirements", my todo list becomes part of the documentation. It belongs there!

I start with a template something like this

# project title

project description

# project requirements

* [ ] help the user with x
* [x] help the user with y
* [ ] help the user with z

# dev notes

## note A

foo

## note B

bar