[PROPOSAL] Add workflow that prepares a PR to deploy to prod

[dblock]

What/Why

What are you proposing?

Instead of having a human open a PR to deploy to prod like #12, add a workflow that opens a PR every time main changes. This will allow any maintainer to merge that PR with a single click to deploy to prod.

What users have asked for this feature?

Every maintainer of this repo.

What problems are you trying to solve?

Currently someone (a maintainer) has to open the PR manually, which takes time. It also prevents that maintainer to deploying to prod because they cannot approve their own PR.

What is the developer experience going to be?

There will always be a PR ready to deploy to prod.

Are there any security considerations?

A maintainer will be able to deploy whatever is in prod at any time.

[nateynateynate]

I'm all for this - sometimes waiting around for another maintainer is problematic.

[nateynateynate]

I'm going to leave this open until I see the workflow operating properly a few times.