docs(readme): link to deployed documentation (#959)

## Summary

* Replace README documentation links that point to the removed local
`docs/` tree.
* Point users to the deployed documentation site at
`https://ananke-documentation.netlify.app/`.
* Keep section-specific links for installation, getting started,
configuration, customisation, and troubleshooting.

## Notes

The corresponding content files live in `gohugo-ananke/documentation`
and build to the deployed documentation site paths used in this README
update.

Closes #957.