Registers a selector for connection drag on the instance. This is a newer version of the
makeSource functionality that has been in jsPlumb since the early days. With this approach, rather than calling
makeSource on every element, you can register a CSS selector on the instance that identifies something that is common to your elements. This will only respond to mouse events on elements that are managed by the instance.
addSourceSelector(selector: string, params?: BehaviouralTypeDescriptor, exclude?: boolean): SourceSelector;
|selector||string||CSS3 selector identifying child element(s) of some managed element that should act as a connection source.|
|params||BehaviouralTypeDescriptor||Options for the source: connector type, behaviour, etc.|
|exclude||boolean||If true, the selector defines an 'exclusion': anything _except_ elements that match this.|