Create devcontainer for development and debugging

[Noordsestern]

If we have a devcontainer, contributors would not need to recreate the test workflow conditions locally.

• [ ] devcontainer added to repo
• [ ] devcontainer can be used out-of-box in VSCode
• [ ] test cases can be executed in VSCode (devcontainer)

Hint: there is a dockerfile in atest folder. Maybe we can reuse it (and combine it with ci-yml workflow)