Automate the deploy/update when a new pool goes to production

[gndelia]

Whenever we push a new pool to production in vesper-metadata, it would be ideal to automate the process of upgrading the graph.

We could use GitHub's repository dispatch events after merging to master in vesper-metadata to trigger an action in this repo, and automate a PR or similar that updates the subgraph.yml.
It could also push to production env once set (And even after that, publish, though that requires gas)