Draft: add debian/bullseye-alf_req/ debian/bullseye-pyalf_req/

I suggest adding images that satisfy the ALF and pyALF requirements, like these two bullseye images. This saves the juggling of installing packages in the GitLab CI configurations.

What do you think, @fgoth?

debian/bullseye-alf_req/Dockerfile

+# A script that adds ALF requirements on top of a basic bullseye install
+FROM git.physik.uni-wuerzburg.de:25812/z03/pdi/debian:bullseye-minbase
+
+RUN apt-get update && \
+    apt-get install --yes --no-install-recommends \
+    # Minimal dependencies for ALF
+    make \
+    gfortran \
+    libblas-dev \
+    liblapack-dev \
+    python3 \
+    # For downloading ALF source code
+    git \
+    ca-certificates \
+    # MPI
+    libopenmpi-dev \
+    # For testsuite
+    cmake \
+    # For downloading and compiling HDF5
+    curl \
+    libghc-zlib-dev \
+    g++ \
+    && \
+    apt-get clean && rm -rf /var/lib/apt/lists/*