Windows version of the ocamllsp wrapper script

[gridbugs]

We install a posix shell script wrapping ocamllsp so that running simply ocamllsp will build and run ocamllsp via dune in an environment where ocamlformat and ocamlformat-rpc (also built with dune) are in PATH (as needed by ocamllsp). We need a version of this for windows. This will be considered working when setting up vscode according to the instructions on https://preview.dune.build/ results in a working ocamllsp.