cri_vm: add xrandr and term_size

Signed-off-by: James Landrein <james@cri.epita.fr>

docs/cri_vm.md

@@ -85,3 +85,20 @@ You need to enable Vt-x or AMD-V in your BIOS.
 
 Go to the VM settings window and in the `System` page and `Processor` tab,
 uncheck the `Enable nested Vt-x/AMD-V` box.
+
+## Small tips for a better environment
+
+### Screen resolution
+You can use the command `xrandr` to change the resolution.
+
+You can see the available resolutions with `xrandr` as following :
+![resolution](assets/resolution.png)
+
+You can change it using `xrandr --output Virtual-1 --auto --mode WIDTHxHEIGHT`
+![xrandr](assets/xrandr.png)
+
+### Term size
+A command line program allows you to change the font size in your terminal.
+
+You can use it with `term_size SIZE`. SIZE being the font size (12, 14, ...
+for instance)