FEATURE gpt researcher template (#13062)

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

templates/research-assistant/README.md

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+# research-assistant
+
+This template implements a version of  
+[GPT Researcher](https://github.com/assafelovic/gpt-researcher) that you can use
+as a starting point for a research agent.
+
+## Environment Setup
+
+The default template relies on ChatOpenAI and DuckDuckGo, so you will need the 
+following environment variable:
+
+- `OPENAI_API_KEY`
+
+And to use the Tavily LLM-optimized search engine, you will need:
+
+- `TAVILY_API_KEY`
+
+## Usage
+
+To use this package, you should first have the LangChain CLI installed:
+
+```shell
+pip install -U langchain-cli
+```
+
+To create a new LangChain project and install this as the only package, you can do:
+
+```shell
+langchain app new my-app --package research-assistant
+```
+
+If you want to add this to an existing project, you can just run:
+
+```shell
+langchain app add research-assistant
+```
+
+And add the following code to your `server.py` file:
+```python
+from research_assistant import chain as research_assistant_chain
+
+add_routes(app, research_assistant_chain, path="/research-assistant")
+```
+
+(Optional) Let's now configure LangSmith. 
+LangSmith will help us trace, monitor and debug LangChain applications. 
+LangSmith is currently in private beta, you can sign up [here](https://smith.langchain.com/). 
+If you don't have access, you can skip this section
+
+
+```shell
+export LANGCHAIN_TRACING_V2=true
+export LANGCHAIN_API_KEY=<your-api-key>
+export LANGCHAIN_PROJECT=<your-project>  # if not specified, defaults to "default"
+```
+
+If you are inside this directory, then you can spin up a LangServe instance directly by:
+
+```shell
+langchain serve
+```
+
+This will start the FastAPI app with a server is running locally at 
+[http://localhost:8000](http://localhost:8000)
+
+We can see all templates at [http://127.0.0.1:8000/docs](http://127.0.0.1:8000/docs)
+We can access the playground at [http://127.0.0.1:8000/research-assistant/playground](http://127.0.0.1:8000/research-assistant/playground)  
+
+We can access the template from code with:
+
+```python
+from langserve.client import RemoteRunnable
+
+runnable = RemoteRunnable("http://localhost:8000/research-assistant")
+```