Create CI workflow

[hohwille]

In the repo we should have GitHub action workflow that runs the build so before we merge, we can see if nothing breaks.
Example of such workflow from IDEasy:
https://github.com/devonfw/IDEasy/blob/main/.github/workflows/build-pr.yml

Requirements:

• for every new PR created or when PR is updated, the workflow runs and we can see the status
• if the status is red, merge of PR is blocked
• frontend is build and tests are run by the workflow
• backend is build and tests are run by the workflow