Add a "Countdown" block

I would like to add a countdown to some of our pages, for example an act page. A countdown can bring across the urgency to act.

The "Countdown" block should include at least:

• Date and time to count down to
• A title
• Possibility to hide it when the date is reached
• A message to display once the date is reached

See idea at >> https://planet4.greenpeace.org/idea/add-a-countdown-block/