Release a ESM-only major version

[cossssmin]

@thewebartisan7 as part of an effort to migrate the PostHTML ecosystem to ESM, I'd like to work on a new major release for posthtml-components that would include:

• refactoring code to ESM-only
• require Node.js 18+
• migrate tests to use Vitest
• switch style linting to eslint
• add types

Please let me know if you're OK with this and I'll start work on the PR. Thanks!

[thewebartisan7]

Hey, sound goods to me! Let me know if you need my help with anything.

[cossssmin]

Thanks, will get started and open a PR and we can take it from there 👍