message: Add tabIndex to the button to make it keyboard focusable
diff: @@ -129,6 +129,7 @@ export default class ReactionsRowButton extends React.PureComponent {
  return <span className={classes}
  role="button"
  aria-label={label}
  + tabindex="0"
  onClick={this.onClick}
  onMouseOver={this.onMouseOver}
  onMouseOut={this.onMouseOut}
  