readme: added apt-get install cmd

README.md

@@ -4,6 +4,7 @@ https://i3wm.org/i3status/manpage.html
 
 ## Installation
 
-```{sh}
+```sh
+sudo apt-get install i3status
 git clone git@git.hammerle.me:fphammerle/config-i3status.git $HOME/.config/i3status
 ```