ci: temporary workflow to resolve Electron release versions for PRs

[dsanders11]

This is a temporary workflow in support of @piotrpdev's Google Summer of Code work. Long-term this will be removed from this repo and the code will be refactored to live on electron/release-status, but for now this is the easiest place to put it such that it can be used immediately. Since it is temporary I've kept it isolated entirely to this one file so it doesn't affect anything else in this repo.

Example snippet of how to fetch the content from the latest workflow run is included below. Requires a GitHub token with actions: read perms on electron/website repo.

const AdmZip = require('adm-zip');

const AUTH_HEADER = { Authorization: `Bearer ${ process.env.GH_TOKEN }` };

let resp = await fetch('https://api.github.com/repos/electron/website/actions/artifacts', { headers: AUTH_HEADER });
const latestArtifact = (await resp.json()).artifacts.filter(({ name }) => name === 'resolved-pr-versions').sort((a, b) => a.id > b.id)[0];

resp = await fetch(latestArtifact.archive_download_url, { headers: AUTH_HEADER });
const buffer = Buffer.from(await resp.arrayBuffer());

const zip = new AdmZip(buffer);
const data = JSON.parse(zip.readAsText(zip.getEntries()[0]));

[VerteDinde]

Looks good! One nit question

[VerteDinde]

I am incredibly nitting here, but do we want to pop this into an Electron repo somewhere? If we think this will actually be pretty temporary, I'm okay leaving it

[dsanders11]

It's a valid point to raise! I'm definitely intending for this workflow overall to be pretty temporary (pending practical realities getting int he way), but this line in particular can be super temporary. Once we merge and have one run of the workflow to store an artifact, this line can be removed entirely as the bootstrap step will be complete and shouldn't (unless artifacts somehow all got jettisoned) be needed again.