* Only consider raw command in output match
... else it will not work for localized messages.
Example German output:
```
Führen Sie »apt list --upgradable« aus, um sie anzuzeigen.
```
* added german output test
* make the linter happy
* apt_list_upgradable: Prepend sudo to suggestion if used in command
* Add apt_upgrade rule
This suggests `apt upgrade` after `apt list --upgradable` if there are
packages to upgrade. It pairs well with the `apt_list_upgradable` rule,
which suggests `apt list --upgradable` after `apt update` if there are
packages to upgrade.
* Add apt_upgrade rule to README