docs: v3.5.0 changelog

Author: kozistr

docs/changelogs/v3.4.3.md renamed to docs/changelogs/v3.5.0.md

@@ -5,6 +5,10 @@
 * Support `StableSPAM` optimizer. (#358, #359)
     * [How to Train in 4-Bit More Stably than 16-Bit Adam](https://arxiv.org/abs/2502.17055?)
 * Support `ScheduleFreeWrapper`. (#334, #360)
+* Implement `AdaGC` optimizer. (#364, #366)
+    * [Improving Training Stability for Large Language Model Pretraining](https://arxiv.org/abs/2502.11034)
+* Implement `Simplified-Ademamix` optimizer. (#364, #366)
+    * [Connections between Schedule-Free Optimizers, AdEMAMix, and Accelerated SGD Variants](https://arxiv.org/abs/2502.02431)
 
 ### Update