feat: ✨ Honour roles for items in olists and ulists

[someth2say]

Usually list items do not have extra roles (AsciiDoc does not allow roles in list items as per today), but they can be added via processors.
This PR honour the roles, and inject them into the generated list items.

[mojavelinux]

I don't think style should be supported. It's not relevant for list items. The built-in HTML converter only passes though the role in this case, so we should be consistent with that.

[someth2say]

I don't think style should be supported. It's not relevant for list items. The built-in HTML converter only passes though the role in this case, so we should be consistent with that.

To be true, I don´t ever grasp where the style comes from nor what are its semantics. I just copied classes are assigned to ol/ul nodes.
Consistency is positive, though.

[mojavelinux]

Again, style is not relevant for list items. The style is something that is specific to blocks, and even then only very special blocks like lists (for the marker or numeration style) or the source block (to differentiate it from a listing block). It should not be included in this case as it is not consistent.

[slonopotamus]

Okay, let's drop style, but keep role