disabled attribute should be described as read-only

[prushforth]

The <layer- disabled> attribute is supposed to be read-only, reflecting the state of renderability of the layer content. For instance, if the layer content falls in a zoom range that does not include the map's current zoom, the layer's disabled property should be true.

[prushforth]

I notice this is inconsistent over on the spec too; it's described as read-only on the api, but the attribute description implies it can be set.