layerNamed(obj) resolves to only base layer type.
I'm not sure what the end plan here is but given that the "types" that inherit from `Layer.js` one would assume that when executing the `layerNamed(string)` resolves to the API centric type.

for example

```
context.api().selectedDocument.layerNamed("Page 1").isPage yields true.
context.api().selectedDocument.layerNamed("Artboard 1").isArtboard yields true.
```
