update readme.md

found out more about usage of history command on redhat.com, added this to the repo readme

README.md

@@ -175,6 +175,7 @@ bzw
 ## history
 
 this lists all the commands of the shell you are in, that you have typed in lastly.
+The list consists of the command plus the a number. After have issued history (ususally filtered by grep with piping - see next chapter) you can directly issue one of the displayed commands WITHOUT using the mouse, by entering the an exclamation mark followed by the number of the command.
 
 ## grep