Add recently completed transcriptions to `/queue` message

[TimJentzsch]

Relevant issue: Closes #171

Description:

This adds the 5 most recently completed transcriptions to the /queue message. I think we'll have to optimize our API to make the updates faster, but the info is definitely nice to have.

Screenshots:

Checklist:

• [x] Code Quality
• [x] Pep-8
• [ ] Tests (if applicable)
• [x] Success Criteria Met
• [x] Inline Documentation
• [ ] Wiki Documentation (if applicable)