New Tailwind theme

## 💥 Proposal

This may be belong in the Infima repo, but I strongly suggest Docusaurus consider Tailwind. Tailwind already solves for theming out of the box. It also gives developers much more freedom. You can still re-implement Infima's core classes with tailwind, so this actually wouldn't _need_ to be a breaking change.

The benefits:
- Smaller CSS footprint
- Better theming
- Less custom CSS needed on other pages

## Next Steps

- Start on a new Tailwind preset
- Get it to feature-parity with classic theme

### Have you read the [Contributing Guidelines on issues](https://github.com/facebook/docusaurus/blob/master/CONTRIBUTING.md#reporting-new-issues)?

Yes