Merge branch 'bump-container' into 'master'

Bump container to latest Debian

See merge request !4

context/Dockerfile

-FROM debian:stretch-slim
+FROM debian:bullseye-slim
 
 LABEL maintainer="ethitter"
 LABEL version="1.0"
 
-RUN echo "deb http://security.debian.org/ stretch/updates main" >> /etc/apt/sources.list
+RUN echo "deb http://security.debian.org/debian-security bullseye-security main contrib non-free" >> /etc/apt/sources.list
 
 RUN apt-get update \
     && apt-get -y --no-install-recommends install \