Add a files array to `package.json`
Add a files array to `package.json`

Ensures that only and all of the `lib/` directory will be in the release.
epoberezkin/ajv,YChebotaev/ajv,YChebotaev/ajv,marbemac/ajv,epoberezkin/ajv,MailOnline/ajv,marbemac/ajv,MailOnline/ajv,epoberezkin/ajv