update readme

README.rst

@@ -15,3 +15,19 @@ fibgrid
    :target: http://fibgrid.readthedocs.org/
 
 Creating Fibonacci grid and read pre-computed grids.
+
+Citation
+========
+
+[![Zenodo](https://zenodo.org/badge/DOI/10.5281/zenodo.14187002.svg)](https://doi.org/10.5281/zenodo.14187002)
+
+If you use the software in a publication then please cite it using the Zenodo
+DOI. Be aware that this badge links to the latest package version.
+
+Please select your specific version at https://doi.org/10.5281/zenodo.14187002 to
+get the DOI of that version. You should normally always use the DOI for the
+specific version of your record in citations. This is to ensure that other
+researchers can access the exact research artefact you used for reproducibility.
+
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+http://help.zenodo.org/#versioning