docs: Add logo usage guidelines and attribution requirements

[hnshah]

Addresses #3291

Summary

Adds comprehensive logo usage documentation to help users understand how to properly use and attribute the MLX logo in their projects.

Changes

• Created docs/LOGO_USAGE.md with:
  • Clear MIT License attribution requirements
  • Available formats documentation (PNG light/dark)
  • Recommended attribution examples (Markdown, HTML)
  • Permitted uses and best practices
  • Note about SVG availability (pending)

Why This Helps

Users like the mlx-docs-l10n project maintainer (Issue #3291) need clear guidance on:

1. What license governs the logo
2. How to properly attribute it
3. What formats are available
4. What uses are permitted

This document provides all that information in one place.

Future Work

• An SVG version of the logo could be added later (currently only PNG available)
• Community members interested in creating an SVG can follow the guidelines in this doc

Testing

• Documentation is clear and complete
• Examples are valid Markdown/HTML
• Links work correctly

Closes #3291

[angeloskath]

Thanks for doing all this but I think we won't merge this. We will merge the logos in #3308 so people can have SVG and PDF versions.

This document is one of the few things in this repo that unfortunately cannot come from the community, ie the community cannot state what is and isn't an Apple trademark and so on. I 'll see if we add a similar document next to the logos in #3308 or later.