Add hello.md file

[devin-ai-integration]

Summary

Adds a simple hello.md file to the root of the repository with a basic welcome message.

Review & Testing Checklist for Human

• Confirm this is the intended location for the file (root of repo vs. inside fern/products/ directory)
• Verify if this file should be added to navigation in docs.yml to be visible in the documentation

Notes

This is a minimal markdown file as requested. Note that the file is not currently linked in any navigation configuration, so it won't appear in the published documentation unless added to docs.yml.

Link to Devin run: https://app.devin.ai/sessions/fb09af5810144b939c17bab9431a87e8
Requested by: unknown ()

[devin-ai-integration]

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