Migrate DWD harvestor to Github actions

[joergreichert]

Current state: The DWD harvestor docker image is executed every day in AWS Fargate.

Motivation: In order to simplify the tech stack / reduce costs, the docker image should be executed with GithubActions (the parent project GiessDenKiez already does this). The docker image can be hosted at DockerHub or GitLab.

Future state: AWS Fargate isn't required anymore as the GitHub action has been properly configured.