add biorxiv citation

README.md

@@ -9,6 +9,7 @@ To cite this work, please note the data release used in your work and cite the f
 1. OpenPBTA:
 Shapiro, J.A., Gaonkar, K.S., Spielman, S.J., Savonen, C.L., Bethell, C.J., Jin, R., Rathi, K.S., Zhu, Y., Egolf, L.E., Farrow, B.K., et al. (2023). OpenPBTA: The Open Pediatric Brain Tumor Atlas. Cell Genom., 100340. [10.1016/j.xgen.2023.100340](https://www.cell.com/cell-genomics/pdf/S2666-979X(23)00115-5.pdf).
 2. OpenPedCan:
+Geng, Z. et al. The Open Pediatric Cancer Project. bioRxiv (2024) [10.1101/2024.07.09.599086](https://www.biorxiv.org/content/10.1101/2024.07.09.599086v1)
 DOI for [all releases](https://zenodo.org/search?q=parent.id%3A6473912&f=allversions%3Atrue&l=list&p=1&s=10&sort=version): `10.5281/zenodo.6473912`. 
 
 The OpenPedCan analyses currently include the following datasets, described more fully below: