Add citation section to README

Added citation information for academic use of egglog-python.

Author: saulshanabrook

README.md

@@ -8,3 +8,20 @@ allowing you to use e-graphs in Python for optimization, symbolic computation, a
 Please see the [documentation](https://egglog-python.readthedocs.io/) for more information.
 
 Come say hello [on the e-graphs Zulip](https://egraphs.zulipchat.com/#narrow/stream/375765-egglog/) or [open an issue](https://github.com/egraphs-good/egglog-python/issues/new/choose)!
+
+## How to cite
+
+If you use **egglog-python** in academic work, please cite the paper:
+
+```bibtex
+@misc{Shanabrook2023EgglogPython,
+  title         = {Egglog Python: A Pythonic Library for E-graphs},
+  author        = {Saul Shanabrook},
+  year          = {2023},
+  eprint        = {2305.04311},
+  archivePrefix = {arXiv},
+  primaryClass  = {cs.PL},
+  doi           = {10.48550/arXiv.2305.04311},
+  url           = {https://arxiv.org/abs/2305.04311},
+  note          = {Presented at EGRAPHS@PLDI 2023}
+}