Add YEC 2025 metacard info to donate.torproject.org

@lavamind this ticket will serve to track the image and text that will need to be updated on donate.torproject.org metacard when the year end campaign is launched. @nicob will add graphic when it is ready. We also want to switch the donate.torproject.org/subscribe text during the campaign.

Campaign launch is October 14th, 15:00 UTC