Documentation: Readme.md link to get_api_key.md is broken

[jzadra]

The link to get_api_key.md on the readme (https://github.com/Broccolito/gptr/blob/main/get_api_key.md).https://github.com/Broccolito/gptr/blob/main/README.md#setting-up-api-key) is broken.

[Broccolito]

Thank you for your comments! The open ai website has a pretty detailed explanation with tutorials. I am removing the markdown file from this repository for clarity.