docs: add release notes summary for v5.2 on main page (#3592)

Author: tomaarsen

index.rst

@@ -1,10 +1,11 @@
-.. attention::
-
-   Sentence Transformers is transitioning from `UKP Lab <http://www.ukp.tu-darmstadt.de/>`_ to `🤗 Hugging Face <https://huggingface.co>`_. This formalizes the existing maintenance structure, as Hugging Face has been maintaining the project for the past two years. The project's development roadmap, support, and commitment to the community remain unchanged. Read the `full announcement <https://huggingface.co/blog/sentence-transformers-joins-hf>`_ for more details!
 
 .. note::
 
-   Sentence Transformers v5.1 recently released, bringing the ONNX and OpenVINO backends to SparseEncoder models. Read `SparseEncoder > Usage > Speeding up Inference <docs/sparse_encoder/usage/efficiency.html>`_ to read more about the performance boosts that you can expect, or read the `v5.1 Release Notes <https://github.com/huggingface/sentence-transformers/releases/tag/v5.1.0>`_ for information on the other changes.
+   Sentence Transformers v5.2 recently released, introducing multi-processing for CrossEncoder, multilingual NanoBEIR evaluators, similarity score outputs in `mine_hard_negatives`, Transformers v5 support, and more. Read the `v5.2 Release Notes <https://github.com/huggingface/sentence-transformers/releases/tag/v5.2.0>`_ for more information.
+
+.. attention::
+
+   Sentence Transformers is transitioning from `UKP Lab <http://www.ukp.tu-darmstadt.de/>`_ to `🤗 Hugging Face <https://huggingface.co>`_. This formalizes the existing maintenance structure, as Hugging Face has been maintaining the project for the past two years. The project's development roadmap, support, and commitment to the community remain unchanged. Read the `full announcement <https://huggingface.co/blog/sentence-transformers-joins-hf>`_ for more details!
 
 SentenceTransformers Documentation
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