templates[patch]: Add cohere librarian template (#14601)

Adding the example I build for the Cohere hackathon.

It can:

use a vector database to reccommend books

<img width="840" alt="image"
src="https://github.com/langchain-ai/langchain/assets/144115527/96543a18-217b-4445-ab4b-950c7cced915">

Use a prompt template to provide information about the library

<img width="834" alt="image"
src="https://github.com/langchain-ai/langchain/assets/144115527/996c8e0f-cab0-4213-bcc9-9baf84f1494b">

Use Cohere RAG to provide grounded results

<img width="822" alt="image"
src="https://github.com/langchain-ai/langchain/assets/144115527/7bb4a883-5316-41a9-9d2e-19fd49a43dcb">

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

templates/cohere-librarian/cohere_librarian/library_info.py

@@ -0,0 +1,27 @@
+from langchain.prompts import (
+    ChatPromptTemplate,
+    HumanMessagePromptTemplate,
+    SystemMessagePromptTemplate,
+)
+
+from .chat import chat
+
+librarian_prompt = ChatPromptTemplate.from_messages(
+    [
+        SystemMessagePromptTemplate.from_template(
+            """
+            You are a librarian at cohere community library. Your job is to
+            help recommend people books to read based on their interests and
+            preferences. You also give information about the library.
+
+            The library opens at 8am and closes at 9pm daily. It is closed on
+            Sundays.
+
+            Please answer the following message:
+            """
+        ),
+        HumanMessagePromptTemplate.from_template("{message}"),
+    ]
+)
+
+library_info = librarian_prompt | chat