Transform the Docs Landing page into Frontmatter

[ovflowd]

Enter your suggestions in details:

Right now, the src/pages/docs.tsx is the only page with manual content written all over it. We want to move this page to contents/docs/index.md which would allow it to be also translated with the Language Selector Toggle.

There would be a new category docs, and the Page's contents would use GraphQL (MDX). (Basically, the same approach as from Learn and all other pages).

This would only influence the Landing page of Docs.

[ovflowd]

Done