Fix missing title in citation (AMReX-Combustion#334)

README.md

@@ -145,6 +145,7 @@ To cite PeleLMeX, please use [![Citing](https://joss.theoj.org/papers/10.21105/j
   number = {90},
   pages = {5450},
   author = {Lucas Esclapez and Marc Day and John Bell and Anne Felden and Candace Gilet and Ray Grout and Marc {Henry de Frahan} and Emmanuel Motheau and Andrew Nonaka and Landon Owen and Bruce Perry and Jon Rood and Nicolas Wimer and Weiqun Zhang},
-  journal = {Journal of Open Source Software}
+  journal = {Journal of Open Source Software},
+  title= {{PeleLMeX: an AMR Low Mach Number Reactive Flow Simulation Code without level sub-cycling}}
 }
 ```