Filter transferred issues (so to not display them twice)

[MaxTru]

Describe the feature / what is the problem?

Once an issue is transferred from a repo to another, it is displayed twice in the wuffle board.

In detail: The original issue URI is still valid (e.g., https://github.com/bpmn-io/fake-join/issues/22) but will redirect to the new issue (https://github.com/bpmn-io/internal-docs/issues/178). The old issue cannot be found in the issues of the original repo (https://github.com/bpmn-io/fake-join/issues/). So it seems like that GitHub simply still provides the reference to the issue on API level.

Probably we need to decide whether this is a bug or a feature. IMO we should filter transferred issues.

Steps to Reproduce

1. Transfer an issue to a new repo which is also in scope of the respective wuffle instance
2. Two cards will appear on wuffle both referencing (effectively) the same issue

Environment

• Host (Browser/Node version), if applicable: Brave (Chromium-based)
• OS: Arch Manjaro Linux
• Board version: 0.34.0

[nikku]

Apparently there is a transferred event that we do not integrate with, yet: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows