add docs

docs/llmchain.md

@@ -0,0 +1,50 @@
+The `LLMChain` is a simple chain that takes in a prompt template, formats it with the user input, and returns the response from an LLM.
+
+<br>
+
+![Description](img/single_node/guideline2.png#only-dark){width=50%}
+![Description](img/single_node/guideline.png#only-light){width=50%}
+
+<br>
+
+More information about the [LLMChain](https://python.langchain.com/en/latest/modules/chains/generic/llm_chain.html){.internal-link target=\_blank} can be found in the LangChain documentation.
+
+---
+### ⛓️LangFlow example
+
+![Description](img/llm-chain2.png#only-dark){width=100%}
+![Description](img/llm-chain.png#only-light){width=100%}
+
+<br>
+
+[Download Flow](data/llm_chain.json){: .md-button download="llm_chain"}
+
+<br>
+
+The `PromptTemplate` is a simple template that takes in a product name and returns a prompt. The prompt is used to generate the response from the LLM.
+
+<br>
+
+**Template**:
+
+```txt
+I want you to act as a naming consultant for new companies.
+
+Here are some examples of good company names:
+
+- search engine, Google
+- social media, Facebook
+- video sharing, YouTube
+
+The name should be short, catchy, and easy to remember.
+
+What is a good name for a company that makes {product}?
+```
+
+<br>
+
+For the example, we used `OpenAI` as the LLM, but you can use any LLM that has an API. Make sure to get the API key from the LLM provider. For example, [OpenAI](https://platform.openai.com/){.internal-link target=\_blank} requires you to create an account to get your API key.
+
+<br>
+
+Check out the [OpenAI](https://platform.openai.com/docs/introduction/overview){.internal-link target=\_blank} documentation to learn more about the API and the options that contain in the node.