Implicit values for aria-valuemin and aria-valuemax on the slider role may need more details

[melanierichards]

On PR #946, @mcking65 pointed out that the implicit values for aria-valuemin and aria-valuemax on slider role do not completely mirror those given in HTML for the range input type, which we reference.

Matt's words:

This list is missing the conditions where only one is specified and it invalidates the implicit value of the other. For instance, if aria-valuemax is not specified and aria-valuemin is specified as 200. Or, conversely, if aria-valuemin is not specified and aria-valuemax is set to -1.

I'm not finding at the moment where in HTML this is specified (closest I could find is that in some but not all cases max must not be less than min), but logging this as a separate issue for discussion.