Dockerfile: Add imagemagick and optipng

Dockerfile

@@ -65,6 +65,8 @@ RUN apt-get upgrade -y \
 		cmake \
 		libass-dev \
 		libpcap-dev \
+		imagemagick \
+		optipng \
 	&& rm -rf /var/lib/apt/lists/*
 
 RUN echo "###### Ubuntu Main Repos" > /etc/apt/sources.list && \