Created by: kvsm
Description of the PR
This change adds a build script which uses babel to transpile generated es6 source to es5, such that it can then be used in node projects or published as a package to npm. The babel package is also removed as it is deprecated, and superseded by babel-cli.
See https://github.com/OpenAPITools/openapi-generator/issues/2126#issuecomment-473926663