i18n: Localize lists in prose (e.g. of names) instead of just calling `.join(', ')`

For example, I think in Japanese you would want "1位、2位、3位" instead of "1位, 2位, 3位".

JavaScript has API for this:

```js
new Intl.ListFormat('ja').format(['Chris', 'Greg', 'Alya', 'Zixuan'])
// 'Chris、Greg、Alya、Zixuan'
```

I'm not aware of a nice way to do this in Flutter, though, but I haven't checked in a while.