Add path parameter for dataset ID of repo to update

[alyssadai]

• [x] Check if repo exists
  • [x] if not, error out
• [x] Check if file exists
  • [x] if not, warn but continue
• [ ] Remove example_synthetic.json used for testing

[neurobagel-bot[bot]]

:rocket: Issue was released in v0.1.0 :rocket: