translate .travis.yml’s script part for GH Actions

[thilp]

Replaces our Travis CI integration with GitHub Actions.

Part of #75, which needs a working CI to be merged.

Description

It seems Travis has forgotten everything about this repository, perhaps because no builds were triggered in a long time. Re-adding the Travis integration to this repository requires asking a Zalando admin to give permission (despite being the main maintainer, I’m not repo admin), which may take even longer. Using GitHub Actions is also a way to reduce the number of third-party dependencies.

Differences compared to the old Travis setup:

• Replaced the PyPI password from my personal account (which would no longer work with two-factor auth) with a dedicated upload token.

Types of Changes

What types of changes does your code introduce? Keep the ones that apply:

• Configuration change

[zincr]

🤖 zincr found 1 problem , 1 warning

❌ Approvals
ℹ️ Large Commits
✅ Specification
✅ Dependency Licensing

Details on how to resolve are provided below

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Approvals

All proposed changes must be reviewed by project maintainers before they can be merged

Not enough people have approved this pull request - please ensure that 1 additional user, who have not contributed to this pull request approve the changes.

• ✅ Approved by PR author @thilp
• ❌ 1 additional approval needed
   

Large Commits

Checks all commits for large additions to a single file. Large commits should be reviewed more carefully for potential copyright and licensing issues

This file contains a substantial change, please review to determine if the change comes from an external source and if there are any copyright or licensing issues to be aware of

• ℹ️ poetry.lock had +100 lines of code changed in a single commit
  Please review this file to determine the source of this change