How to add attributes to an entire list or definition list?

[hanwentao]

This issue is about the combination usage of the extension attribute list with the built-in list or the extension definition list. How to add an attribute to the entire list, instead of merely an item? The following code doesn't work (the attribute is applied to the second item):

* a
* b
{: .list}

[waylan]

This is a duplicate of #227.