Add note in RELEASE-NOTES.md

Author: Harivallabha

RELEASE-NOTES.md

@@ -35,6 +35,7 @@ This new version of `Theano-PyMC` comes with an experimental JAX backend which,
 - Change SMC metropolis kernel to independent metropolis kernel [#4115](https://github.com/pymc-devs/pymc3/pull/4115))
 - Add alternative parametrization to NegativeBinomial distribution in terms of n and p (see [#4126](https://github.com/pymc-devs/pymc3/issues/4126))
 - Added semantically meaningful `str` representations to PyMC3 objects for console, notebook, and GraphViz use (see [#4076](https://github.com/pymc-devs/pymc3/pull/4076), [#4065](https://github.com/pymc-devs/pymc3/pull/4065), [#4159](https://github.com/pymc-devs/pymc3/pull/4159), [#4217](https://github.com/pymc-devs/pymc3/pull/4217), and [#4243](https://github.com/pymc-devs/pymc3/pull/4243)).
+- Add Discrete HyperGeometric Distribution (see [#4249](https://github.com/pymc-devs/pymc3/pull/#4249))
 
 ### Maintenance
 - Switch the dependency of Theano to our own fork, [Theano-PyMC](https://github.com/pymc-devs/Theano-PyMC).