Reduce Docker Image Size

[GabrielRF]

If possible, use Python as base image instead of Ubuntu

[hankman13]

In this Dockerfile from the repo synology-surveillance-api-motion-mqtt-gifs their are using the image from jrottenberg/ffmpeg:4.1-alpine and added python. I think it's a good starting point and you just have to add/change your python file and requirements to the provided Dockerfile.