feat: add issue to the output

[marstamm]

Proposed Changes

This PR adds the issue JSON as an output. This ensures we can use any relevant details in later steps. Most relevant for my use case is the Issue nr, so we can automatically assign Milestones to the release issue

related to https://github.com/camunda/camunda-modeler/issues/4311

Checklist

To ensure you provided everything we need to look at your PR:

• [x] Brief textual description of the changes present
• [ ] Visual demo attached
• [ ] Steps to try out present, i.e. using the @bpmn-io/sr tool
• [x] Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}