docs: v3.0.0 changelog

Author: kozistr

docs/changelogs/v3.0.0.md

@@ -1,6 +1,14 @@
 ## Change Log
 
-Major version is updated! (`v2.12.0` -> `v3.0.0`) (#164)
+The major version is updated! (`v2.12.0` -> `v3.0.0`) (#164)
+
+Many optimizers, learning rate schedulers, and objective functions are in `pytorch-optimizer`.
+Currently, `pytorch-optimizer` supports **67 optimizers (+ `bitsandbytes`)**, **11 lr schedulers**, and **13 loss functions**, and reached about 4 ~ 50K downloads / month (peak is 75K downloads / month)!
+
+The reason for updating the major version from `v2` to `v3` is that I think it's a good time to ship the recent implementations (the last update was about 7 months ago) and plan to pivot to new concepts like training utilities while maintaining the original features (e.g. optimizers). 
+Also, rich test cases, benchmarks, and examples are on the list!
+
+Finally, thanks for using the `pytorch-optimizer`, and feel free to make any requests :)
 
 ### Feature