Add labels to Docker images

Dockerfile

@@ -22,4 +22,9 @@ WORKDIR /app
 
 COPY . .
 
+LABEL org.opencontainers.image.source=https://git.wtf-eg.de/kompetenzinventar/ki-backend.git
+LABEL org.opencontainers.image.url=https://git.wtf-eg.de/kompetenzinventar/ki-backend
+LABEL org.opencontainers.image.documentation=https://git.wtf-eg.de/kompetenzinventar/ki-backend#docker
+LABEL org.opencontainers.image.vendor="WTF Kooperative eG"
+
 CMD ["python3", "run_prod.py"]