docs: v3.4.2 changelog

Author: kozistr

docs/changelogs/v3.4.2.md

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+### Change Log
+
+### Feature
+
+* Implement `SCION` optimizer. (#348, #352)
+    * [Training Deep Learning Models with Norm-Constrained LMOs](https://arxiv.org/abs/2502.07529)
+
+### Docs
+
+* Fix `AliG` optimizer visualization. (#350)
+
+### Contributions
+
+thanks to @AidinHamedi