feature: Restore link to Cortex repo

[evaline-ju]

Restore links to https://github.com/rossoctl/cortex

[rubambiza]

@justinmacnair Was this ever resolved?

[esnible]

We previously had a button on the main page, next to "Get Started", that lead to https://github.com/rossoctl/cortex

We removed that again, recently, because the docs for that repo aren't ready. This issue is to restore that link, or to sync those docs onto the main page.

[evaline-ju]

Note we've archived the original description's repo mention: https://github.com/kagenti/plugins-adapter. I'll update the description with the above