Fixes + Install some Julia packages

Dockerfile-CI

 # A docker file for building the image on GitLab's CI
 FROM mambaorg/micromamba:latest
 COPY --chown=$MAMBA_USER:$MAMBA_USER . /tmp/binder
+
+# Install files
+RUN cp -ra install_file/* /opt/conda/
+
+# Install conda packages
 RUN cd /tmp/binder && \
     micromamba install -y -n base -f environment.yml && \
     micromamba clean --all --yes && \
-    /usr/local/bin/_entrypoint.sh pip cache purge && \
-    cp mydocker_entrypoint.sh /opt/conda/bin/mydocker_entrypoint.sh && \
-    cp -ra install_file/* /opt/conda/
+
+# Install Julia packages
+RUN /usr/local/bin/_entrypoint.sh julia -e 'using Pkg; Pkg.add(["SymPy", "Symbolics", "Plots", "Widgets", "IJulia"])'
     
 RUN rm -rf /tmp/binder