feat: dynamic import, dual module (#149)

BREAKING CHANGE: must always call `await validator.init()` prior to first use, no path
to sync usage remains. Furthermore instead of using require() + cache busting via delete
it will now use dynamic import

* feat: dynamic import for schema files, only async init
* feat: dual-module
* chore: increase node version for CI

fix: upgrade deps

fix: missing semantic-release

chore: .gitignore

fix: omit field when undefined

fix: upgrade deps (#138)

feat: use draft-2019-09 (#137)

feat: ajv@8

BREAKING CHANGE: some error message wordings changed, updated to newest json schema draft

fix: dep

fix: include all formats by default