[core] better jsdoc support ATTRIBUTES

[thepassle]

Fixture:

class MyElement extends HTMLElement {
  static get observedAttributes() {
    return [
    /** some jsdoc */ // only description
    "placeholder",
    /**
     * Disabled the component // description goes here, or after the type. 
     * @type {disabled} 
     * @type {disabled} - Disables the component // If this is present, override the description above
     * @property disabled // adds a `"fieldName": "prop1"` to the attr in the output CE.json
     */
    "disabled",
    ];
  }
}

• [x] make sure it works for static get observedAttributes() {}
• [x] make sure it works for static observedAttributes = []
• [x] make sure the @property related fieldName doesnt clash with the support for the @property jsdoc
• [x] make sure it supports a @type jsdoc
• [x] make sure a @type's description overwrites the 'top' description
• [x] add example in docs
• [x] Deal with jsdoc type imports ${import('./module.js').SomeEvent}. Get type SomeEvent, add reference to ./module.js
• [x] merge or override with JSDoc declared above the class