APIs missing: set Fills blending options

[matteogratton]

Similarly to the Opacity, this option is not currently available in the APIs:

Currently, it is possible to set them only via: layer.style.sketchObject.fills()[1].contextSettings().setBlendMode(13);

It would be nice to have something like: layer.style.fills[value].blendMode = "Overlay"

It is also missing a way to read the option: layer.style.sketchObject.fills()[1].contextSettings().blendMode();