How to avoid layer name repetition?

Once we have that `layer("LayerName")` "accessor", we would still have to write
`let LayerName = layer("LayerName")` to have a variable called LayerName for use with withLayers. Otherwise you would have to write `withLayers([layer("LayerName")], ...)`, which is both wordy and typo-prone (if you type `withLayers([layer("LayerNaem"], ...)` a new layer would be created).
