Allow configuration for final newline

[ussu]

Hi 👋🏼

When running ember-intl-analyzer --fix with JSON translation files, I realised that the formatter trims final newline in translation files

From what I understand by reading the code, this is due to these few lines
Parsing the JSON trims the newline

It would be great if we could add the newline back into the file :)

updatedTranslations = JSON.stringify(translations, null, 2) + '\n';

This would make the behaviour consistent with YAML translation files, since YAML.stringify adds a final newline

In case there are people relying on the newline trimming, maybe we can add this as a configuration param, what do you think?

// config

export default {
  removeFinalNewline: true | false;
}

// index.js

updatedTranslations = JSON.stringify(translations, null, 2);
updatedTranslations += options.removeFinalNewline? '' : '\n';