Demo and API docs

##<iron-a11y-announcer>

iron-a11y-announcer is a singleton element that is intended to add a11y to features that require on-demand announcement from screen readers. In order to make use of the announcer, it is best to request its availability in the announcing element.

Example:

Polymer({

  is: 'x-chatty',

  attached: function() {
    // This will create the singleton element if it has not
    // been created yet:
    Polymer.IronA11yAnnouncer.requestAvailability();
  }
});

After the iron-a11y-announcer has been made available, elements can make announces by firing bubbling iron-announce events.

Example:

this.fire('iron-announce', {
  text: 'This is an announcement!'
}, { bubbles: true });

Note: announcements are only audible if you have a screen reader enabled.