Create webhook and CI status for StorageServer caching

[staticfloat]

To address issues around storage server caching delay, we should preload new resources into the storage server by triggering a CI run on PRs to General. I'm thinking we have a webhook that triggers the StorageServer into caching any new resources mentioned in the current pull request, and then if they all get cached successfully, we push a status to the PR that sets a passing status to that CI status.

This should allow us to pre-fill the storage server's cache so that when the PR is merged, the resources are already stored.