[css-forms-1] It seems like "slider" controls need more details about the rendering and input

[mfreed7]

The css-forms-1 spec says a lot about slider controls, but it seems to be missing some details about how the rendering takes place. For example, the thumb is rendered (magically at the moment) at a relative position that indicates the value of the control. It is also responsive to mouse and keyboard input to manipulate that position, and therefore the value. These details need to be defined precisely, I think, so the behavior can be interoperable.