(How) should we archive previous model versions?

[damonbayer]

Or generally keep track of forks of models.

[dylanhmorris]

I propose using Github releases to pin meaningful model versions.

A few wrinkles / questions

• I think we will want to limit the number of actively maintained/run models at any one time.
• How many "models" do we consider this repo to have? Is each "Pyrenew-{}" a model in this context?