adding citation details

README.md

@@ -6,7 +6,21 @@
 
 **Authors:** Derod Deal (dealderod@ufl.edu), Néstor Espinoza (nespinoza@stsci.edu)
 
-`spelunker` is a package that assists on studying JWST FGS/NIRISS guidestar data. Check out our [readthedocs](https://jwst-fgs-spelunker.readthedocs.io) for detailed documentation.
+`spelunker` is a package that assists on studying JWST FGS/NIRISS guidestar data. Check out our [readthedocs](https://jwst-fgs-spelunker.readthedocs.io) for detailed documentation. 
+
+**If you make use of `spelunker`, please [cite our paper](https://joss.theoj.org/papers/10.21105/joss.06202) (Deal & Espinoza, 2024, JOSS, 9(97), 6202):**
+
+    @article{Deal2024, 
+             doi = {10.21105/joss.06202}, 
+             url = {https://doi.org/10.21105/joss.06202}, 
+             year = {2024}, publisher = {The Open Journal}, 
+             volume = {9}, 
+             number = {97}, 
+             pages = {6202}, 
+             author = {Derod Deal and Néstor Espinoza}, 
+             title = {Spelunker: A quick-look Python pipeline for JWST NIRISS FGS Guide Star Data}, 
+             journal = {Journal of Open Source Software} 
+    }
 
 <a href="https://joss.theoj.org/papers/1547289b35b16a5d2955b20ed3945a2e"><img src="https://joss.theoj.org/papers/1547289b35b16a5d2955b20ed3945a2e/status.svg"></a>
 
@@ -98,4 +112,4 @@ This project is under the MIT License, which can be viewed [here](https://github
 
 ## Acknowledgments
 
-DD and NE would like to thank the STScI's Space Astronomy Summer Program (SASP) as well as the National Astronomy Consortium (NAC) program which made it possible for them to work together on this fantastic project!
+DD and NE would like to thank the STScI's Space Astronomy Summer Program (SASP) as well as the National Astronomy Consortium (NAC) program which made it possible for them to work together on this fantastic project!