Migrate to ES modules

[Lutymane]

• I already searched past issues
• I already checked the wiki/TODO page

Is your feature request related to a problem? Please describe.

CommonJS is morally obsolete and it's hard to write some complex plugins and logic with this limitation (like reusing logic between SMTP and Web server written in modern code). Not talking about lack of top-level await in cjs

Describe the solution you'd like

Migrate code base to ES modules

[msimerson]

Since moving from CommonJS to ESM is a moral imperative to you, we expect you'll be leading the effort. We look forward to all the PRs you will be submitting to convert our entire code base. I'd recommend starting at the very bottom and working your way up. haraka-tld would be a great place to start.