Add binder setup to the cookiecutter

[ianhi]

trafficstars

It would be nice to have a binder badge in the readme and the appropriate postBuild file premade.

[jtpio]

Sounds good :+1:

For reference this was added to the JupyterLab extension cookiecutter as opt-in here: https://github.com/jupyterlab/extension-cookiecutter-ts/pull/64