This was missing after migrating to i3 via nix.
i3blocks was installed via apt before.
home-manager doesn't provide options, I keep my old file. It is updated
for the used version.
Install and configure i3 via nix home-manager.
This commit just migrates existing configuration.
It doesn't clean things up, e.g. move stuff to expected locations.
I configure x* tools from within i3 right now …
Also didn't clean things up, e.g. sort and group related things.