Update README.md to include arXiv link closes #269 (#270)

Author: zdaq12

README.md

@@ -6,6 +6,7 @@ PyPartMC is a Python interface to [PartMC](https://lagrange.mechse.illinois.edu/
   a particle-resolved Monte-Carlo code for atmospheric aerosol simulation.
 PyPartMC is implemented in C++ and it also constitutes a C++ API to the PartMC Fortran internals.
 The Python API can facilitate using PartMC from other environments - see, e.g., Julia example below.
+For an outline of the project, rationale, architecture, and features, refer to: [D'Aquino et al., 2023 (arXiv)](https://doi.org/10.48550/arXiv.2308.02052) (please cite if PyPartMC is used in your research).
 
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