add ffmpeg

add install ffmpeg for video

setup/photoprism-install.sh

@@ -76,6 +76,7 @@ apt-get install -y gnupg &>/dev/null
 apt-get install -y make &>/dev/null
 apt-get install -y zip &>/dev/null
 apt-get install -y unzip &>/dev/null
+apt-get install -y ffmpeg &>/dev/null
 msg_ok "Installed Dependencies"
 
 msg_info "Setting up Node.js Repository"