Add release date

Author: remlapmot

NEWS.md

@@ -1,6 +1,6 @@
 # TwoSampleMR v0.6.13
 
-(Release date 2025-##-##)
+(Release date 2025-03-26)
 
 * Added `mr_grip()` function which implements the MR-GRIP (modified MR-Egger with the Genotype Recoding Invariance Property) method of Dudbridge and Bowden et al. (2025).
   The new method can be accessed by `mr(dat, method_list = "mr_grip")` or it can be added to the default list of methods with `mr(dat, method_list = c(subset(mr_method_list(), use_by_default)$obj, "mr_grip"))`.