Migrate docs to docusaurus, Store docs for all past versions in main

[srdtrk]

Description

This PR:

• Migrates the docs to docusaurus.
• Uses the docs theme from cosmos-sdk.
• Allows navigation to ADRs from the navbar.
• This PR also stores docs for past versions in main. - WIP
• Update style guides. - WIP

closes: #3492

addresses: #3488

Commit Message / Changelog Entry

docs: migrate to docusaurus, store versioned docs and sidebars in main

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• Targeted PR against correct branch (see CONTRIBUTING.md).
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
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• Wrote unit and integration tests.
• Updated relevant documentation (docs/) or specification (x/<module>/spec/).
• Added relevant godoc comments.
• Provide a commit message to be used for the changelog entry in the PR description for review.
• Re-reviewed Files changed in the Github PR explorer.
• Review Codecov Report in the comment section below once CI passes.

[srdtrk]

Moving to feat branch instead