Update README with GPT-4 usage details

This commit adds information about the usage of GPT-4 and GPT-3.5 in the AICodeBot tool. It explains the differences between the two and provides guidance on how to choose the appropriate version based on the user's needs and OpenAI account capabilities. A link to the GPT-4 API waitlist is also included for users whose accounts do not currently support GPT-4.

Author: TechNickAI

README.md

@@ -61,7 +61,11 @@ Commands:
 
 The first time you run it, you'll be prompted to enter your OpenAI API Key, which is required, as we use OpenAI's large language models for the AI. You can get one for free by visiting your [API key settings page](https://platform.openai.com/account/api-keys").
 
-Pro tip: You can also set the `OPENAI_API_KEY` environment variable to your API key, and it will use that instead of prompting you.
+#### GPT-3.5 vs GPT-4
+
+When using AICodeBot, you have the option to use either GPT-3.5 or GPT-4. While GPT-4 can often provide more accurate and detailed responses, GPT-3.5 is faster and might be sufficient for simpler tasks. We highly recommend GPT-4.
+
+Not all OpenAI accounts have GPT-4 API access enabled. By default, AICodeBot will use GPT-4 if your OpenAI account supports it, we will check the first time you run it. Tip: If your OpenAI API does not support GPT-4, you can ask to be added to the waitlist [here](https://openai.com/waitlist/gpt-4-api)
 
 ## Roadmap of Upcoming Features