Use .jsbeautifyrc file as user settings

Would it be possible to have the option of using a configuration file (`.jsbeautifyrc`) for the JS Beautifier settings? See [Loading settings from environment or .jsbeautifyrc (JavaScript-Only)](https://github.com/beautify-web/js-beautify#loading-settings-from-environment-or-jsbeautifyrc-javascript-only)

This allows you to define different format options per directory, or have 1 configuration file for all projects by putting it in your project root folder.

I also don't like having the settings under "codeformatter_js_options" because then it doesn't inherit the default settings. For example, if you want to only define `format_on_save` to true:

```
{
"codeformatter_js_options": {
"format_on_save": true
}
}
```
you then get the error "Formatter not found" because you didn't define the "syntaxes" option.

I feel like this plugin could be really powerful, but these two issues (mainly the configuration file one) is stopping me from using it.