Add built-in support for n98-Magerun2 in the deploy container

[MagicLegend]

Is your feature request related to a problem? Please describe.
Magerun2 solves some annoyances devs have to deal with when developing with Magento. Directly running cronjobs for example.

Describe the solution you'd like
Would be great if the deploy container (so the cli php images) now used for magento commands would also support running n98-magerun2. For example:

docker-compose run --rm deploy magerun2 <command>

Note that magerun2 will also expose the regular Magento CLI, so it could also be used as a replacement of the magento-command command.

Describe alternatives you've considered
Fixing the container myself locally. But that means my colleagues would have to go through the same steps as well. Changing it at the source would be a better solution IMO.

Additional context
Magerun2 is under the MIT licence, so license wise I think it should be fine to distribute the Magerun binary directly in the container.

The original https://github.com/meanbee/docker-magento2 already had this exact functionality. Perhaps most (all?) of what is needed can be taken from that repository.