create julia dummy files first launch

if we don't have this then when user launch Julia for the first time, their project would be read-only, see ref: https://github.com/JuliaLang/Pkg.jl/issues/3039

another place where we can fix this is in

/cvmfs/sft-nightlies.cern.ch/lcg/views/dev4/Tue/x86_64-centos7-gcc10-opt/etc/julia/startup.jl

currently empty. but idk if that will interfere with cluster use etc.