A query-only layer should be distinguished accessibly and by style, or other means, in the layer control

[prushforth]

Currently a layer can be created that contains only a <link rel=query> template, meaning it doesn't draw anything, but it will return features or info from a server on interaction.

It is not distinguished in the layer control at this time, and in fact it will be disabled if it doesn't have an templates or or features for rendering (the latter is a bug, imo).

So, it should be styled and announced such that it is distinguished as query-only. Further, it should not be disabled, but should be interactive in the layer control, like any other layer, as long as it is in bounds.

[AliyanH]

Query layer only works now if the layer is not hidden in #909. Still need a way to style the layer in the layer control to let the screenreader and visual readers know that the layer is or contains a map-extent that has a query aspect to it.

I believe we should use the help of an icon or something similar in the layercontrol to let the users know that the layer is queryable: