Please indicate which design pattern among singleton, observer, bridge, abstract factory, faade, mediator, proxy, you would use to find the solution in below systems. Briefly explain your reason. Just the design pattern name wont get any point

Question : You would like to design a system which has an online file that contains details about every piece of content a site has published. Each time a site publishes a new piece of content, details about that content are automatically generated and should be send to the subscribers of the site