Please fix declension in relative time

[VBagmut]

Describe the bug
Thanks for fixing #577. But I found another bug. This time with relativeTime plugin.

Expected behavior
It is incorrectly using declension. For example: "2 dayjs ago" needs to be "2 дня назад" but instead shows "2 дней назад". How it needs to be described here http://www.unicode.org/cldr/charts/28/supplemental/language_plural_rules.html#ru
I hope you will fix this and then I'll be able to throw away heavyweight momentjs. Because now I need to use moment for this cases.

Information

• Day.js: 1.8.14
• OS: Ubuntu 18.04.2 LTS
• Browser: Google Chrome 74.0.3729.169 (Official Build) (64-bit)
• Time zone: GMT+03:00

[moosemanf]

Same in German...

altough it's elegant in english, it is not possible in german:

d.en.relativeTime = {
    future: 'in %s',
    past: '%s ago',
    y: 'a year',
    yy: '%d years'
  }

  if (withoutSuffix) return out
    return ((result > 0) ? loc.future : loc.past).replace('%s', out)

we would need (for example) a yy for withoutSuffix == true and another yy for withoutSuffix == false

withoutSuffix

3 Jahre

withSuffix

vor 3 Jahren

#304 there is a good starting solution, but unfortunately no progress...

[stalkerg]

I am also interested in that feature. It's completely unnatural for Slavic languages (and rule a little bit more complicated than in English).