Organize documents and serve document homepage from '/docs'

[jeremychoi]

• Publish document home from the '/docs' directory, leveraging docsify. The end result looks like: https://redhatproductsecurity.github.io/rapidast/.
• docs/README.md will be shown in the github repo home

All the links from the documentation home and the repo should work.

When this is merged, the Github pages configuration will be changed to deploy docs from the development branch.