Make dedicated (cookiecutter) branch for research projects

[nstarman]

I propose a permanent branch of package-template for research projects.

Research projects would benefit from following a standardized layout and building off the nice features in this template package. In a fork, I've been building a project template -- https://github.com/nstarman/project_template to accomplish this in my own work.

The main added features are:

• more project-oriented documentation and files in doc
• notebooks and scripts folders
• a scratch folder
• an envs folder for storing virtual environments associated with the project

As an example, https://macro-lightning.readthedocs.io/en/latest/ is a recent project of mine that used this template.

@astrofrog et al., I would be more than happy to work on this / help maintain long-term.

[astrofrog]

@nstarman - thanks for proposing this! We'll need to have a think about it as it might make more sense to just keep it outside the astropy organization but link to it (e.g. 'if you are interested in a template for a research project you might instead want to check out [link]'). We're trying to avoid accumulating too much in the astropy organization because even if you are able to help maintain it for now, it would still require commitment on our part to help maintain it or take over the maintenance in future if you are no longer able to maintain it (and we are stretched very thin at the moment). I'll see what the other maintainers think!

[pllim]

https://github.com/astropy/package-template#deprecation-warning