fix: set permissions for webapp/public/images

Author: Dup4

docker/domserver/scripts/start.d/50-domjudge.sh

@@ -173,6 +173,7 @@ then
 fi
 
 # Set up permissions
+chown -R www-data: /opt/domjudge/domserver/webapp/public/images
 chown www-data: etc/dbpasswords.secret
 chown www-data: etc/restapi.secret
 if [[ -f etc/symfony_app.secret ]]