Update readme, include LlamaIndex (openai#457)

* cr

* cr

README.md

@@ -84,6 +84,7 @@ People are writing great tools and papers for improving outputs from GPT. Here a
 - [PromptPerfect](https://promptperfect.jina.ai/prompts): A paid product for testing and improving prompts.
 - [Weights & Biases](https://wandb.ai/site/solutions/llmops): A paid product for tracking model training and prompt engineering experiments.
 - [OpenAI Evals](https://github.com/openai/evals): An open-source library for evaluating task performance of language models and prompts.
+- [LlamaIndex](https://github.com/jerryjliu/llama_index): A Python library for augmenting LLM apps with private data (personal, organizational).
 
 ### Prompting guides