Meteor-accounts-t9n (t9n) with language variants

Thanks to a rainy day and the inspiration from Mozilla Fluent selecotrs t9n has a new version 2.5.1. The new feature allows for singular/plural or sex handling. This ticket describes how to use it.

I created also a demo project where parameters for selectors can be modified interactively, there is a demo app and source available.

The demo is a simple Vue app, without Meteor as there is no backend and so it could be hosted on Github Pages. The usage would be identical in a Meteor app, no matter if frontend or backend.