Add NEWS bullet

Author: DavisVaughan

NEWS.md

@@ -1,5 +1,9 @@
 # vctrs (development version)
 
+* `vec_ptype()` is now generic. The default behavior for S3 classes continues
+  to use `vec_slice(x, 0L)`, but S3 methods can now be written to improve
+  performance as required for custom classes.
+
 * Fixed an issue where `vctrs_rcrd` objects were not being proxied correctly
   when used as a data frame column (#1318).