Merging default subs with languages is not implemented for all langs

[Dobrosław Żybort]

Looks like default substitutions are not running for some langs:

slug/languages_substitution.go

Line 10 in aba3e10

 for _, sub := range []*map[rune]string{&deSub, &enSub, &plSub, &esSub} { 

More tests needed and fixing it in a way that will not force adding every lang by hand.