Update README.md

Author: Jashcraf

README.md

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 [![DOI](https://zenodo.org/badge/513353061.svg)](https://zenodo.org/badge/latestdoi/513353061)
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 Poke (pronounced /poʊˈkeɪ/ or po-kay) is a ray-based physical optics module for Python. It's named this because the name encodes the k-vector (which we are raytracing!) and the E-vector (which we are propagating!). Also I came up with the name before lunchtime, when I was craving fish from [Suisan](https://www.suisan.com/our-services/fish-market/).