Update quickstart doc: add cookiecutter installation prerequisite

docs/docs/quickstart.md

@@ -6,6 +6,8 @@ In this page you will learn how to set up a project using the cookiecutter. The
 
 ### Project Configurer
 
+_**Prerequisite**: If this is your first time setting up a cookiecutter project you need to install it from https://pypi.org/project/cookiecutter. You can do this in the terminal with `brew install cookiecutter`._
+
 1. **Request repository setup**: First things first, you need a repo created for you. Submit a [Create a repo in the Nesta GitHub org](https://github.com/nestauk/github_support/issues/new/choose) issue from the [github_support](https://github.com/nestauk/github_support) issue page. You will need to provide a project name, suggested repo name, whether public/private, github teams involved, team leading the project, short and long description of the project. An empty repo will be set up for you and you will receive a notification when this is done.
 
 2. **Set up your project locally**: It is important that you _do not clone the repo yet!_ Instead, follow these steps: