Add commands in vim guide for network and lock

- nmtui for network
- i3lock for locking their computer

Guides/i3.md

@@ -5,3 +5,11 @@ Best keyboard efficient windows manager
 ## Install
 
 Launch script `Install/i3-install`.
+
+## Lock your screen
+
+Use the _dmenu_ and use the **i3lock** program.
+
+## Activate a wifi connection
+
+Start the **nmtui** program in a terminal.