Feature request: update single package

[tobiasBora]

For now, we can either update all packages at once, or to upgrade a package, we need to uninstall + reinstall the package, but the UI provides no way to directly upgrade it, even if it detects it in the "Update" tab. It might also be helpful to know what "update" actually do: is it upgrading the channel and redoing a nix-env -iA? What happens when using flake? etc… Maybe via a tooltip displayed when hovering?