elementIsVisible() {
    const info = "elementIsVisible has been temporarily DEPRECATED as it was not working correctly and a fix is complex";
    log("error", "uib:elementIsVisible", info)();
    this.send({ payload: "elementIsVisible has been temporarily DEPRECATED as it was not working correctly and a fix is complex" });
    return false;
  }
DEPRECATED FOR NOW - wasn't working properly.
Is the chosen CSS Selector currently visible to the user? NB: Only finds the FIRST element of the selection.
Requires IntersectionObserver (available to all mainstream browsers from early 2019)
Automatically sends a msg back to Node-RED.
Requires the element to already exist.
@returns {false} False if not visible