Allow PRs to soft-publish

[antazoey]

Overview

for the purpose of demo-ing docs PRs, it'd be nice if we had a way to demo a PR's docs, like have it spin up a temporary published build docs/_build/<pr-number>

Specification

Maybe have it get triggered from PR-title directives like

docs: [publish-demo] New docs work

then we can detect that spin it up.
On merge to main or cancel, we would have to trigger the deleting of that folder

Dependencies

Include links to any open issues that must be resolved before this feature can be implemented.

[linear]

APE-1811 Allow PRs to soft-publish