Export the Rule class so that it's possible to add custom rules.
Make the custom button apply the styles defined in the icon theme and add isToggled function to determine whether the button should apply the toggled style. Also, allow the button to be further customizable by defining a custom builder implementation.
Fix the demo pages and add a demo page showcasing a custom attribute.
* Moved all embed code to seperate folder
* Consolidated embed builders
* Moved embed toolbar items out
* Moved embed code to separate package
* Updated imports
* Removed I from interface names
* Refactored embed button implementation
* Update readme