deepseek, docs: chatdeepseek integration added (#29445)

libs/partners/deepseek/README.md

@@ -0,0 +1,24 @@
+# langchain-deepseek-official
+
+This package contains the LangChain integration with the DeepSeek API
+
+## Installation
+
+```bash
+pip install -U langchain-deepseek-official
+```
+
+And you should configure credentials by setting the following environment variables:
+
+* `DEEPSEEK_API_KEY`
+
+## Chat Models
+
+`ChatDeepSeek` class exposes chat models from DeepSeek.
+
+```python
+from langchain_deepseek import ChatDeepSeek
+
+llm = ChatDeepSeek(model="deepseek-chat")
+llm.invoke("Sing a ballad of LangChain.")
+```