doc/usage/linux: Add i3wm section [ci skip]
doc/usage/linux: Add i3wm section [ci skip]

nono/cozy-desktop,nono/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop