Add comments regarding tab-index=-1

Author: t3chguy

src/components/views/messages/DateSeparator.js

@@ -57,6 +57,7 @@ export default class DateSeparator extends React.Component {
 
  render() {
  // ARIA treats <hr/>s as separators, here we abuse them slightly so manually treat this entire thing as one
+ // tab-index=-1 to allow it to be focusable but do not add tab stop for it, primarily for screen readers
  return <h2 className="mx_DateSeparator" role="separator" tabIndex={-1}>
  <hr role="none" />
  <div>{ this.getLabel() }</div>

src/components/views/rooms/EventTile.js

@@ -787,6 +787,7 @@ module.exports = createReactClass({
  this.props.permalinkCreator,
  'replyThread',
  );
+ // tab-index=-1 to allow it to be focusable but do not add tab stop for it, primarily for screen readers
  return (
  <div className={classes} tabIndex={-1}>
  <div className="mx_EventTile_msgOption">