[Julia] Add a Julia client generator

Description

We want to add a new generator for Julia client. A good starting point is https://github.com/JuliaComputing/Swagger.jl

Ref: https://julialang.org/

openapi-generator version

Latest master

Suggest a fix/enhancement

If anyone wants to help on this, please reply to let us know.

cc @log0ymxm, @tanmaykm