Add citing information

Author: Datseris

CITATION.bib

@@ -0,0 +1,12 @@
+@article{Datseris2018,
+  doi = {10.21105/joss.00598},
+  url = {https://doi.org/10.21105/joss.00598},
+  year  = {2018},
+  month = {mar},
+  volume = {3},
+  number = {23},
+  pages = {598},
+  author = {George Datseris},
+  title = {DynamicalSystems.jl: A Julia software library for chaos and nonlinear dynamics},
+  journal = {Journal of Open Source Software}
+}