add release note

Author: wpbonelli

doc/ReleaseNotes/develop.toml

@@ -77,4 +77,9 @@ description = "Fix the PRT PRP package's DRAPE option's behavior. A draped parti
 [[items]]
 section = "fixes"
 subsection = "basic"
-description = "Previously, GWF model output files could only be referenced by a single coupled model's FMI package. This might be necessary for certain configurations where multiple transport models or particle tracking models in the same simulation need flow information from a previous GWF simulation. Referencing the same GWF output files from multiple coupled models would cause a crash. Fix file-opening logic to allow multiple coupled models to refer to the same GWF model's output files."
+description = "Previously, GWF model output files could only be referenced by a single coupled model's FMI package. This might be necessary for certain configurations where multiple transport models or particle tracking models in the same simulation need flow information from a previous GWF simulation. Referencing the same GWF output files from multiple coupled models would cause a crash. Fix file-opening logic to allow multiple coupled models to refer to the same GWF model's output files."
+
+[[items]]
+section = "features"
+subsection = "model"
+description = "Previously PRT model particle events were written to output file(s) immediately. By default, PRT will now buffer events in memory before writing them to disk. Introduce a new option for the PRT Output Control (OC) package, SCRATCH\\_BUFFER, which enables buffering events in scratch files instead of memory. This can avoid out-of-memory errors at the price of increased file IO and runtime."