Update NEWS.md

Author: fabern

NEWS.md

@@ -5,6 +5,8 @@
   easier processing within cost-functions. Default cost-functions were updated,
   but currently ignore the names. This is fully backward compatible, but allows
   to use the names in user-created cost functions.
+* P-model was updated internally to use jmax and vcmax temperature dependencies 
+  from Kumarathunge et al. (2019) instead of Kattge & Knorr (2007)
 
 # rsofun 5.1.0