Move to ESM

[LitoMore]

Changes

• Move to Pure ESM (here is why)
• Require Node.js 18 (since we moved to ESM)
• Ignore package-lock.json (here is why)
• Use GitHub Actions
• Change linting, testing and coverage library to modern tools: XO, AVA, c8, and tsd
• Add type definitions
• Remove invalid Travis CI badge