Add postgres rules for CodeQL

[Minigugus]

CodeQL is an advanced code analysis tool, which is now part of Github.

pg is already supported by CodeQL, maybe postgres could also have its own rules ?

[porsager]

Oh yeah, that's really interesting!

I suppose that would require a PR to the CodeQL repo, so if anyone feels up for the task, maybe mention this issue in the PR ? 🙂