Migrate building and testing from Travis to Github Actions

[willianpaixao]

Rationale

Why should this feature exist?

Github Actions is now the de facto tool for building, testing and publishing open source projects hosted in Github. It has integrations with the Github's UI and PR review process, giving more clarity and transparency about the builds and tests on every push or pull request.

Additionally, Travis no longer has free credits in open source projects, so this migration would reduce costs.

Implementation

Do you have ideas regarding the implementation of this feature?

Yes, it's essentially a translation from the current .travis.yml to one or a few smaller files in the .github/workflow directory, following Github's reference manuals. This guide is very helpful.

Are you willing to implement this feature?

Yes, 100%. I just need to know if the feature is desired and the PR wold be accepted be the team.

[holiman]

Migrating from travis to GH actions is just migrating from one vendor lock-in to another vendor lock-in. We might aswell stay with travis until we've built our own in-house CI system, which is in the works.

@holiman So the in-house CI is now live?