Add new locale: Japanese

[nielsmaerten]

Translations

• [x] New translations approved on Crowdin
• [x] Translations merged into master and www branch
• [x] If Routines are supported, locale code added to lngsSupportingRoutines array
• [x] www branch deployed to GitHub Pages
• [ ] Translator credit added to README / package.json

Google Review requirements

• [ ] Prepare for deployment - Google's Checklist

Highlights:

• [x] Privacy policy fully translated
• [x] Display name and Invocation consistent across site, Action and Directory info
• [x] Directory information up-to-date
• [ ] Testing instructions up-to-date

Testing

• [ ] Invocation works in the new language
• [ ] Tested on real device in alpha

General deployment

• [ ] master branch deployed to Firebase
• [ ] Dialogflow fullfilment url pointing to Firebase Function