feat: simplify and add changelog

[urmauur]

Describe Your Changes

• Modify the placement of the navbar menu.
• Add an announcement banner.
• Update the “Download from GitHub” button in the hero section.

• Added changelog page

• Detail changelog page

Context changes code

• Pulled all releases from GitHub during SSR.
• Listed all changelog releases (excluding drafts and prerelease).
• Created a page for each changelog and displayed the body returned from the API as Markdown
• u can run yarn create:changelog for generate the file

Fixes Issues

• Closes feat: Simplify site for Cortex.cpp #197
• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[github-actions]

Preview URL: https://0f601259.cortex-docs.pages.dev

[gabrielle-ong]

LGTM - great work on the changelog @urmauur
@dan-homebrew requested to remove the "self-hosted alternative to OpenAI platform" above hero banner - Ill follow with a small PR