docs: add utility script for merging SD3 weights into a single .safetensors file

Author: kohya-ss

README.md

@@ -14,6 +14,10 @@ The command to install PyTorch is as follows:
 
 ### Recent Updates
 
+Mar 6, 2025:
+
+- Added a utility script to merge the weights of SD3's DiT, VAE (optional), CLIP-L, CLIP-G, and T5XXL into a single .safetensors file. Run `tools/merge_sd3_safetensors.py`. See `--help` for usage. PR [#1960](https://github.com/kohya-ss/sd-scripts/pull/1960)
+
 Feb 26, 2025:
 
 - Improve the validation loss calculation in `train_network.py`, `sdxl_train_network.py`, `flux_train_network.py`, and `sd3_train_network.py`. PR [#1903](https://github.com/kohya-ss/sd-scripts/pull/1903)