Allow per instance settings

I'm the maintainer of the Colorbox Field Formatter module and I see that colorbox is about to change direction in the D8 a bit and I can perfectly understand why this is happening and I'm supporting this.

However, to allow other modules to extend your module it would be great to have a small enhancement in your JS code. Where you're calling .colorbox(settings.colorbox) it would be great if you could optionally merge the settings with some attributes provided as markup for the instance. That way, other modules could provide their additional settings for each instance without the main colorbox module to be modified.

I'd be happy to provide a patch for that but wanted to ask first, if you would be considering to merge this into your module.