event decorator for components

[muratcorlu]

Lit doesn't provide any convention for defining and publishing component events but it seems logical to at least create our own. So events of the component will be more visible and we'll avoid code duplication for firing multiple events from many components.

class GrIcon extends LitElement {
   ....
   @event('gr-load') load: EventEmitter<string>;

So for me, requirements are:

• A common function/class to fire type-safe component events with optional parameters (bubbles, cancellable).
• A decorator that accepts optional event name. By default it can use kebab-cased version of the class property name.