improve docs

Author: ivelichkovich

docs/reference/gc-commandline-reference.md

@@ -35,6 +35,15 @@ Print version and exit.
 
 The pagination size to use when calling api-server to list nodefeatures. 
 Pagination is useful for controlling the load on api-server/etcd as the nodefeature resources can be large.
+A value of 0 will disable pagination.
+
+Default: 200
+
+Example:
+
+```bash
+nfd-gc -list-size=100
+```
 
 ### -gc-interval