Make GitHub dependency graph work with Cog

[bfirsh]

It'd be neat if Cog models showed up in the dependency graph: https://github.com/replicate/cog/network/dependents?package_id=UGFja2FnZS0yMzY0Njk0NzI2

This seems to happen when people put cog in requirements.txt: https://github.com/Andbecode/clip_draw_wave/blob/master/requirements.txt

I wonder if we can automatically do this as part of cog init, perhaps without a version so that it can get overridden with the correct version when building. 🤔

/cc @zeke

[mattt]

@bfirsh GitHub recently introduced a dependency graph submission API that allows 3rd parties that can do this. Previously, there was no way to directly control what showed up in the dependency graph.

It's not a perfect solution, but we could register a GitHub Actions workflow on initialization that runs a custom action (TBD by us) that determines the model version and sends that through GitHubs's new API.