docs: vmmap - added note regarding gef cache values

docs/features.md

@@ -102,6 +102,13 @@ Read/Write/Execute.
 
 ![xinfo-example](https://pbs.twimg.com/media/CCSW9JkW4AAx8gD.png:large)
 
+**Important note** : `gef` will as much as possible automatically refresh its
+own cache to avoid relying on obsolete information of the debugged
+process. However, in some dodgy scenario, `gef` might fail detecting some new
+events making its cache partially obsolete. If you notice an inconsistency on
+your memory mapping, you might want to force `gef` flushing its cache and
+fetching brand new data, by running the command `reset-cache`.
+
 
 ## `heap` command ##