New Documentation for Cortex

[ramonpzg]

This PR includes the following

• New landing page
• New Model Hub
• New documentation site

The documentation site follows the Diataxis methodology where the docs are split into 4 sections:

• How-to, which includes installation, quickstart tutorial, configuration and more
• Explanations: covers the architecture of cortex and details related to how it handles models, engines, and the server
• Tutorials: As of now, there are only two tutorials but there is a mini video series coming soon
• Reference: contains CLI commands and other low level details regarding cortex

The new model hub has two sections, one for cortex with the same models as those in the old website, and a section for selected hugging face models

The recommended way to test the docs is with bun js.

[github-actions]

📝 Documentation Preview: https://menloresearch.github.io/cortex.cpp/

[vansangpfiev]

Added some comments. Should we remove ONNX Runtime in docs since cortex does not support it?

[selim1903]

Mostly docs, so I leave it to Sang to approve. no core code change