Including a CLI wrapper for the SDK

[rf-santos]

Medium CLI

I am submitting this pull request to integrate a CLI wrapper for the Python SDK.
This will simplify usage of the Medium API and SDK in CI/CD pipelines, for instance, using github actions.
This way, if I want to use an action to publish an .md file, I would simply pass the self-issued access token from github secrets to the CLI and call the SDK client to publish it.

medium create-post "My Title" /path/to/post.md -T <MEDIUM_ACCESS_TOKEN>

This would also facilitate publishing directly from the command-line.