Supports a <reversed-counter-name> value type for counter-reset.
This value instantiates a reversed counter of the given <counter-name> with a starting value of the given <integer>, or no starting value if not given.
The absence of the reversed() function makes developers couldn't use the modern, intuitive syntax.
With proper support for the reversed() syntax, styling countdowns and other descending lists is now as simple and reliable as it should be.