Feature: folder based versioning

[orkunkl]

Hey,

As you know CosmWasm uses this theme for the documentation website: https://docs.cosmwasm.com/
Recently it got more difficult to maintain multiple versions, because a change to one content needs to be applied to all branches.
Having a docusaurus like folder-diff based approach would make lot easier for us: https://docusaurus.io/docs/versioning

[tac0turtle]

I would love this feature!!.@lovincyrus talked about it a few times

[orkunkl]

We decided to migrate to https://docusaurus.io due to great versioning support and multi repo support. We will make sure the structure is similar to cosmos-sdk docs and vuepress-theme-cosmos 👍