add Dagger module

[becojo]

Add a Dagger module to use poutine. I tried to recreate the CLI using Dagger's API as closely as possible.

It's convenient to have Dagger cache poutine's output and manage cloning git repository. For instance, running custom rules in boost-rnd/poutine-rules on actions/github-script can be done like so:

dagger -d call -m github.com/boostsecurityio/poutine \
  --config-src https://github.com/boost-rnd/poutine-rules \
  analyze-local \
  --src https://github.com/actions/github-script

This module is already listed on the Dagger module registry and hopefully brings more visibility to the project.