Add a OCaml client generator

Description

We would like to create an OCaml client generator so that OCaml developers can find it more easily to consume REST APIs.

Similar to how some other generators (e.g. R, Lua, PowerShell) are created, we will use the reverse engineering process to create the OCaml client generator.

• create OCaml petstore samples (implemented at least 2 endpoints to start with: getPetById, addPet)
• create the templates and eng
• test the auto-generated OCaml code and revise the OCaml generator, templates

cc @andrenth

openapi-generator version

Latest master

Suggest a fix/enhancement

If anyone wants to help on this (e.g. testing, creating templates, etc), please reply to let us know.