* add new addOptions option
* replace defaultOptions with addOptions for all extensions
* replace defaultOptions with addOptions for all demos
* replace defaultOptions with addOptions in docs
* refactoring
* refactoring
* drop object support for addOptions
* fix optional options
* fix tests
I built some extensions based on the textStyle extension but whenever I reset a style/attribute, the whole textStyle mark gets removed when there are still other styles defined in the mark.