feat: add GPT link in top bar

[MdechampG]

This PR aims at adding an external link to the top bar towards the OKP4 GPT.

Do you agree to name it "OKP4 GPT" or should we put "Oracle Druid"

Summary by CodeRabbit

• New Features
  • Introduced a new navigation link to the chat page for OKP4 GPT.
• Documentation
  • Added a new sidebar entry for "OKP4 GPT" with a direct link to the chat interface.

[coderabbitai[bot]]

Walkthrough

The updates include adding a new navigation link to the Docusaurus configuration, which directs users to the OKP4 GPT chat page on the OpenAI website. Additionally, the sidebar configuration now features a new section for the OKP4 GPT, providing quick access to the related chat page.

Changes

Files	Change Summary
docusaurus.config.js	Added a navigation link to the OKP4 GPT chat page on the left side of the navbar.
sidebars.js	Added a new "OKP4 GPT" entry under the gpt section with a link to the beta chat page.

🐇✨ In the code forest, a link was born,
A path to knowledge, fresh and unsworn.
🌐🔗 To the oracle of AI, it leads,
Where questions meet wisdom and curiosity feeds.
🎉🥕

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