Support GitHub Actions CI config

[swissspidy]

Feature Request

• [x] Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

When scaffolding package tests I can only add a config for Travis CI and nothing else.

I would say the majority of developers has moved on from Travis CI to using GitHub Actions.

Describe the solution you'd like

Support GitHub Actions as a CI provider, and perhaps even make it the default.

[slaFFik]

When scaffolding package tests I can only add a config for Travis CI and nothing else.

Technically you can add circleci as well (with a --ci=circle flag).