This PR improves the `/fetch` command with better support for URLs that return JSON content. JSON response bodies will now be pretty-printed and placed within a Markdown code block: <img width="690" alt="Screenshot 2024-06-10 at 3 39 52 PM" src="https://github.com/zed-industries/zed/assets/1486634/4a7c1cb7-9f5b-4a63-9e8e-5168bf9a6625"> Release Notes: - Improved the handling of JSON response bodies in the `/fetch` command in the Assistant.