kanshi: add package to home.packages

[GaetanLepage]

Description

Currently, enabling services.kanshi does not make the kanshi executable on the user $PATH.
Although the goal of this module is providing a systemd service for kanshi, it can still be useful to run the software manually from time to time.
For instance, this can be used to manually select a profile.

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

cc @nurelin

[nurelin]

Ok for me.

[rycee]

Thanks! Merged to master now 🙂