Merge pull request #15 from RayStick/README-cite

Update README.md

Author: RayStick

README.md

@@ -2,6 +2,7 @@
 [![All Contributors](https://img.shields.io/badge/all_contributors-4-orange.svg?style=flat-square)](#contributors-)
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+To cite this repository, please see: 
 [![DOI](https://zenodo.org/badge/223283087.svg)](https://zenodo.org/badge/latestdoi/223283087)
 
 PsychoPy code to display visual instructions for a _Breath Hold_ and a _Cued Deep Breathing_ task, alongside MRI scanning.