include vi updates

NEWS.md

@@ -4,9 +4,11 @@
 
 * Re-worked how progress is printed to console when `verbose_progress` is `TRUE`, following the design of `ranger`. Messages now indicate the action being taken, the % complete, and the approximate time until finishing the action. 
 
+* Improved variable importance, following the design of `ranger`. Importance is now computed tree-by-tree instead of by aggregate. Additionally, mortality is the type of prediction used for importance with survival trees, since mortality does not depend on `pred_horizon`.
+
 * Allowed multi-threading to be performed in `orsf()`, `predict.orsf_fit()`, and functions in the `orsf_vi()` and `orsf_pd()` family.
 
-* Allowed for sampling without replacement and sampling a specific fraction of observations in `orsf()`
+* Allowed sampling without replacement and sampling a specific fraction of observations in `orsf()`
 
 * Included Harrell's C-statistic as an option for assessing goodness of splits while growing trees.