[feature]: Give access to the 'blocking', 'blocked by', 'relates to' etc. fields in the plane API

[jaivinraj]

Is there an existing issue for this?

• [X] I have searched the existing issues

Summary

When making an API call to /api/v1/workspaces/:slug/projects/:project_id/issues/, blocking, blocked by, relates to and duplicate of should be returned as fields in the results section of the response for each issue

Why should this be worked on?

• These fields are incredibly important for project planning, as they can help to ascertain the order of tasks that need to happen (eg. A is blocked by B and B is blocked by C ➡️ C should be done first).
• Personally, I would like to be able to extract the data via the API, so that I can create a dependency graph for my project