feat(markdown-preview): Migrate editor and renderer services to ESM

[hivanalejandro]

Description

Fixes b/253601199

Checklist

• [x] I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• [x] Tests pass: npm test (see Testing)
• [x] Lint pass: npm run lint (see Style)
• [x] Please merge this PR for me once it is approved