title: Add intellisense in VS2017 for html attributes and element
body: <p>I'm using VS2017 (with new Salsa Javascript Language service) for a project with angularJS, creating html components.
  I have js-doc installed, which help me a lot with intellisense for js classes.
  I want to add intellisense for my custom elements with custom attributes.
  Exemple:
  I create an element:
  ax-dropdown-popup, with attributes: datasource, item-id-field, item-display-field,popup-relative-left, etc.</p>
  
  <p><strong>What I need to do to have intellisense with theses attributes when I create an html element ax-dropdown-popup?</strong></p>