Provide easy UI to set "poster of the week"

[christophfriedrich]

Sometimes we have very important posters, like for the Geoparty. The current method to ensure that they get more attention is to either add the file to the plakate folder multiple times or to set up a news entry with HTML code that shows the image permanently in a box. I prefer the latter method and would like to provide an easier UI to achieve it.

One idea could be to automatically display such a box for every poster that contains a keyword like WICHTIG or GEPINNT or STICKY in its filename.