Create Handler instance
a Handler object
Used for parse R Markdown and lift into command line interface, Dockerfile, Docker container, and cwl json.
dockerfileHandlera function or NULL, how you handle Dockefile, for example, push it to GitHub.
dockerHandlera function or NULL, how you handle local docker container, for example, push it to DockerHub.
cwlHandlera function or NULL, how you handle cwl json file or yaml file, for example, push it to SevenBridges platform as an app.