Add missing juliapkg.json to dockerfile

Dockerfile

@@ -25,6 +25,7 @@ RUN pip3 install --no-cache-dir -r /pysr/requirements.txt
 # We do a minimal copy so it doesn't need to rerun at every file change:
 ADD ./pyproject.toml /pysr/pyproject.toml
 ADD ./setup.py /pysr/setup.py
+ADD ./juliapkg.json /pysr/juliapkg.json
 ADD ./pysr /pysr/pysr
 RUN pip3 install --no-cache-dir -e .