readme : add FreeChat (#4248)

Author: psugihara

README.md

@@ -117,6 +117,7 @@ as the main playground for developing new features for the [ggml](https://github
 - [oobabooga/text-generation-webui](https://github.com/oobabooga/text-generation-webui)
 - [withcatai/catai](https://github.com/withcatai/catai)
 - [semperai/amica](https://github.com/semperai/amica)
+- [psugihara/FreeChat](https://github.com/psugihara/FreeChat)
 
 ---