copy env.yml in docker

Dockerfile

@@ -2,6 +2,7 @@ FROM docker.io/condaforge/miniforge3
 
 LABEL maintainer="CTA-LST - https://github.com/cta-observatory"
 
-RUN conda env update -n base -f environment.yml
+COPY environment.yml /tmp/environment.yml
 
-RUN conda clean -a
+# Update the base environment and clean up in one layer to reduce image size
+RUN conda env update -n base -f /tmp/environment.yml && conda clean -afy