Add release notes for v0.2.1

Author: bvandermoon

docs/release_notes.md

@@ -22,6 +22,13 @@ MaxText is [available in PyPI](https://pypi.org/project/maxtext/) and can be ins
 
 ## Releases
 
+### v0.2.1
+* Use the new `maxtext[runner]` installation option to build Docker images without cloning the repository. This can be used for scheduling jobs through XPK. See the [MaxText installation instructions](https://maxtext.readthedocs.io/en/maxtext-v0.2.1/install_maxtext.html) for more info.
+* Config can now be inferred for most MaxText commands. If you choose not to provide a config, MaxText will now [select an appropriate one](https://github.com/AI-Hypercomputer/maxtext/blob/9e786c888cc7acdfc00a8f73064e285017e80b86/src/maxtext/configs/pyconfig.py#L51-L67).
+* Configs in MaxText PyPI will now be picked up without storing them locally.
+* New features from DeepSeek-AI are now supported: Conditional Memory via Scalable Lookup ([Engram](https://arxiv.org/abs/2601.07372)) and Manifold-Constrained Hyper-Connections ([mHC](https://arxiv.org/abs/2512.24880)). Try them out with our [deepseek-custom](https://github.com/AI-Hypercomputer/maxtext/blob/9e786c888cc7acdfc00a8f73064e285017e80b86/src/maxtext/configs/models/deepseek-custom.yml) starter config.
+* MaxText now supports customizing your own mesh and logical rules. Two examples guiding how to use your own mesh and rules for sharding are provided in the [custom_mesh_and_rule](https://github.com/AI-Hypercomputer/maxtext/tree/9e786c888cc7acdfc00a8f73064e285017e80b86/src/maxtext/configs/custom_mesh_and_rule) directory.
+
 ### v0.2.0
 
 # Changes
@@ -52,4 +59,4 @@ Our first MaxText PyPI package is here! MaxText is a high performance, highly sc
 
 Users can now install MaxText through pip, both for local development and through stable PyPI builds. Please see our [MaxText Installation Guide](https://maxtext.readthedocs.io/en/latest/install_maxtext.html) for more setup details.
 
-Going forward, this page will document notable changes as we release new versions of MaxText.
+Going forward, this page will document notable changes as we release new versions of MaxText.