Add option to read configuration from a file

[apoblock]

The configuration options currently can be specified only via command line - it will be useful to allow using a configuration file. The format could look like this:

{
  "templateDelimiters": [ ["{", "}"] ],
  "attributes": [ "alt", "placeholder", "title", "label", "friendly-message" ],
  "ignoreTags": [ "style", "script", "pre", "code" ],
  "include": [ "**/mycomponents/**/*.html", "myfile.html5" ],
  "exclude": [ "**/__mytests__/**/*.html", "test1.html" ]
}

Additional CLI parameters would be needed --config name of the configuration file (with default to something like .i18n-lint.json), and --init - allowing to generate basic config file.