Have CTA or template for adding metadata about the tap

We probably don't want to do this during the cookiecutter part of the SDK, but as part of the #TODO checklist it'd be good to prompt users to update a YAML file and png for their connector.

We could have a template yml and png file that are built by the cookiecutter and fill it out based on what we know. Then using #254 (closed) users could update it in place. Then for submission to the Hub they could update it further. If everything lived in their repo, perhaps under a .singer directory, we could just pull that info for the hub with only a simple MR for them to update.