chore: update readme (#45)

Author: shigma

packages/core/README.md

@@ -4,4 +4,7 @@
 
 A Meta-Framework of Spatiotemporal Composability.
 
-**Cordis is under active development. The API is not yet stable and may change without notice. Documentation and paper is coming soon.**
+**Cordis is under active development. The API is not yet stable and may change without notice.**
+
+- Paper: [_A Programming Paradigm for Spatiotemporal Composability_](https://github.com/cordiverse/paper)
+- Documentation: [cordis-primer](https://deepseek-harness.github.io/deepseek-harness/reference/cordis-primer)