Provide option to integrate with eslint

[tobiasso85]

Integration with eslint is possible by using the CLIEngine of eslint.

E.g. by providing an output json which looks like the result expected by eslint and then using the eslint formatter to format the result.

See:

• https://eslint.org/docs/developer-guide/nodejs-api#clienginegetformatter
• https://eslint.org/docs/developer-guide/nodejs-api#cliengineexecuteonfiles

Since CLIEngine is deprecated:

• https://eslint.org/docs/developer-guide/nodejs-api#-formatter-type
  can be used