add support for v4 plural

[4rthem]

Allow to use defaultValue_other with compatibilityJSON v4

[dm-xai]

This addition would be awesome.

Sadly, it doesn't handle <Trans/> component

          <Trans
            i18nKey="testMsg"
            count={2}
            tOptions={{
              defaultValue_one: 'You have a message.',
              defaultValue_other: 'You have {{count}} messages.',
            }}
          />

[4rthem]

@dm-xai It's working correctly on my side.

[alexanderbh]

Get this merged please. I tested it and it works. It does not work without these changes. I don't understand how people say it works. It does not.

The code here is the code that actually creates the keys. And without this change it simply does not look at the defaultValue_one or defaultValue_other attributes. They are ignored.