Migrating a project from GitLab CI, setting up GitHub Actions

[Sander Striker]

Hi,

For anyone interested in following along, or providing any guidance or
help: we're looking to migrate BuildStream (see:
https://petri.apache.org/projects)  from GitLab to GitHub, including moving
from GitLab CI to GitHub Actions (https://s.apache.org/3tp4q
).

Cheers,

Sander