Contributing models / making it easier to load from a local directory

I ran an experiment on prompthero/openjourney-v2 to compile it for coreml. I also put that on huggingface to make it work with the Diffusers App. It would be really nice to make this process easier as well as let users point to their own local models rather than downloading from HG. Would you like a more robust contribution for this feature?

For reference:

* I used https://github.com/apple/ml-stable-diffusion to convert the models. Probably worth a script to make the process easier.
* https://huggingface.co/dcolish/coreml-openjourney-v2 is the model repo.
* I edited ModelInfo class to add it. Its pretty straightforward.