(un)highlight on focusin and focusout

[pkra]

Currently highlighting remains when the element loses focus.

IIRC it is intentional not to reset the aria-active-descendant (much like MathJax's a11y extensions), but I find the visual highlight disorienting.

It seems better UX to run unhighlight when focusout occurs and set run highlight again when focusin occurs.

[pkra]

Here's some simple code

  node.addEventListener('focusin',function(event){
    let navigator = chromify.navigators[event.target.id];
    chromify.highlight(navigator.active);
  });
  node.addEventListener('focusout',function(event){
    let navigator = chromify.navigators[event.target.id];
    chromify.unhighlight(navigator.active);
  });

[pkra]

For the new version:

 constructor(node, tree) {
    this.node = node;
    this.tree = tree;
    this.node.addEventListener('keydown', this.move.bind(this));
+   this.node.addEventListener('focusin', this.highlight.bind(this));
+   this.node.addEventListener('focusout', this.unhighlight.bind(this));
  }