Carsten Heidmann authored Jun 24, 2020 and femiadeyemi committed Jun 30, 2020

change trigger for the push. It should only be executed when something has been pushed to the master branch.

Motivation:
* add minimal CI so that we have a build on push and PRs

Modification:
* add minimal workflow configuration so that we have a Maven build after push or PRs

Result:
* a Maven build is being executed after push or PRs and the CI badge is being shown in the README.md