Merge pull request #33 from nschloe/add-doi

add doi

Author: nschloe

CITATION.cff

@@ -0,0 +1,10 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Schlömer"
+  given-names: "Nico"
+  orcid: "https://orcid.org/0000-0001-5228-0946"
+title: "matplotx: Extensions for Matplotlib"
+doi: 10.5281/zenodo.5985269
+url: https://github.com/nschloe/matplotx
+license: MIT

README.md

@@ -6,6 +6,7 @@
 [![PyPi Version](https://img.shields.io/pypi/v/matplotx.svg?style=flat-square)](https://pypi.org/project/matplotx/)
 [![Anaconda Cloud](https://anaconda.org/conda-forge/matplotx/badges/version.svg?=style=flat-square)](https://anaconda.org/conda-forge/matplotx/)
 [![PyPI pyversions](https://img.shields.io/pypi/pyversions/matplotx.svg?style=flat-square)](https://pypi.org/project/matplotx/)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.5985269.svg)](https://doi.org/10.5281/zenodo.5985269)
 [![GitHub stars](https://img.shields.io/github/stars/nschloe/matplotx.svg?style=flat-square&logo=github&label=Stars&logoColor=white)](https://github.com/nschloe/matplotx)
 [![Downloads](https://pepy.tech/badge/matplotx/month)](https://pepy.tech/project/matplotx)