Further GitHub integration

[crutchcorn]

There's a few features that would be amazing to have as a user:

1. GitHub PR comments (like Vercel):

2. GitHub "Deployments" integration

3. GitHub checks reporting to show status of deploy from the commit/pull request (also enables blocking PR merges until SST deploy passes)

These would go a long way to help the DX of SST Console feel even more amazing/premium