Update README.md

Add a release note to announce the MaxText PyPI package

Author: bvandermoon

README.md

@@ -67,6 +67,7 @@ After installation, you can verify the package is available with `python3 -c "im
 
 * \[September 26, 2025\] Vocabulary tiling ([PR](https://github.com/AI-Hypercomputer/maxtext/pull/2242)) is now supported in MaxText! Adjust config `num_vocab_tiling` to unlock more efficient memory usage, see [doc](https://maxtext.readthedocs.io/en/latest/explanations/tiling.html).
 * \[September 24, 2025\] The GPT-OSS family of models (20B, 120B) is now supported.
+* \[September 15, 2025\] MaxText is now available as a [PyPI package](https://pypi.org/project/maxtext). Users can now [install maxtext through pip](https://github.com/AI-Hypercomputer/maxtext?tab=readme-ov-file#from-pypi-recommended).
 * \[September 5, 2025\] MaxText has moved to an `src` layout as part of [RESTRUCTURE.md](RESTRUCTURE.md). For existing environments, please run `pip install -e .` from MaxText root.
 * \[August 13, 2025\] The Qwen3 2507 MoE family of models is now supported: MoEs: 235B Thinking & 280B Coder as well as existing dense models: 0.6B, 4B, 8B, 14B, and 32B.  
 * \[July 27, 2025\] Updated TFLOPS/s calculation ([PR](https://github.com/AI-Hypercomputer/maxtext/pull/1988)) to account for causal attention, dividing the attention flops in half. Accounted for sliding window and chunked attention reduced attention flops in [PR](https://github.com/AI-Hypercomputer/maxtext/pull/2009) and [PR](https://github.com/AI-Hypercomputer/maxtext/pull/2030). Changes impact large sequence configs, as explained in this [doc](https://github.com/AI-Hypercomputer/maxtext/blob/main/docs/guides/performance_metrics.md)