Update README.md - add a link to the paper and ask to cite it.

README.md

@@ -4,6 +4,17 @@
 
 Local Z Projector is an ImageJ2 plugin to perform local-Z projection of a 3D stack, possibly over time, possibly very large.
 
+## Citation.
+
+If you use this work for your Research, please cite the paper it is described in:
+
+> __DProj: A toolbox for local 2D projection and accurate morphometrics of large 3D microscopy images.__
+> 
+> Sébastien Herbert, Léo Valon, Laure Mancini, Nicolas Dray, Paolo Caldarelli, Jérôme Gros, Elric Esposito, Spencer L. Shorte, Laure Bally-Cuif, Romain Levayer, Nathalie Aulner, Jean-Yves Tinevez
+> 
+> bioRxiv 2021.01.15.426809; doi: https://doi.org/10.1101/2021.01.15.426809
+
+
 ## Installation.
 
 LocalZProjector is a [Fiji](https://fiji.sc/) plugin and can be installed directly within the [Fiji updater](https://imagej.net/ImageJ_Updater).