- Integrated relevant content from catalogd/README.md into the project's main README by adding Demo and Quick-Start steps from catalogd/README.md to the main README.
- Removed the old catalogd/README.md as its remaining content (e.g., contribution guidelines) is already covered in CONTRIBUTING.md.

Co-authored-by: Jordan Keister
Co-authored-by: Per Goncalves da Silva <perdasilva@redhat.com>

…now we have only one service

Co-authored-by: Brett Tofel <btofel@redhat.com>

- Update catalogd/docs/fetching-catalog-contents.md
- Updare docs/tutorials/add-catalog.md