Improove CI/CD-Pipeline

Acceptance Criteria:

The Pipeline should contains the following stages:

• BuildStage
  • npm build
• Deploy-Teststage
  • deploy to teststage (Heroku)
• E2E-test-stage:
  • run e2e-tests
• Unit-Teststage
• Build-Docker-Stage
• Deploy:DockerHub
  • deploy to Dockerhub
• Deploy:Production
  • deploy to productionstage (Heroku)