Migrate from travis to github actions to test build

[dr0i]

Note that the .travis.yml is deliberately not removed as it does more
than just testing the build.

• update badge in README

See #351.

[dr0i]

This branch is reflected by badge https://github.com/metafacture/metafacture-core/workflows/Build/badge.svg?branch=351-migrateFromTravisToGithubActionsToTestBuild . The master's badge is not build yet (it would start by merging this PR) so it cannot be shown at https://github.com/metafacture/metafacture-core/workflows/Build/badge.svg?branch=master.

[dr0i]

@fsteeg : I fixed the wrong reference in the commit message and force pushed. This is now review-ready.

[fsteeg]

Hm, so you mentioned leaving the travis.yml in place since it does more. But then this is not done yet, right?

[dr0i]

The issue is about migrating the "test build", which the PR resolves using github actions.
At travis is more done, trying there to prepare release workflow. Which is not working anymore, anyhow.
We could a) create a new issue where this could be resolve or discussed if it should be resolved or b) remove that functionality altogether here by removing .travis.yml.
What do you think?

[fsteeg]

Right, maybe we should create a new issue. As far as I understand, there are 3 additional things done in the Travis build:

• Run the sonarcloud check (https://sonarcloud.io/dashboard?id=org.metafacture%3Ametafacture-core)
• Build and deploy a GitHub release
• Publish the release to Central

We could discuss in the new issue which of these we want, and how to implement them.

[dr0i]

@fsteeg: I created 3 new issues for implementing 1. SonarCloud checks, 2. building release and 3. publish the release to Central.
So I think you can go on review this issue .