Docker image for bbb-render

During last year’s Covid-19 lock-down here down-under, our Linux and Python meetings were partially held as virtual events. Thanks to the NZOSS, we had access to a BigBlueButton instance, an awesome open-source video conferencing tool. Back then, I didn’t have any luck in converting the presentations into regular video formats using bbb-render. Lawrence managed to get the conversion going on his Debian laptop today. That triggered me to write a Docker image during lunchtime to make the conversions easier, without having to install any software (aside from Docker, of course):