feat: add vercel deploy support & simplify the entire setup

[stipsan]

You can't test it with sanity/create before merging

But you can use this button until then:

When I tried running this earlier today this is what I saw:

logs


At first it was tempting to just see if all the trouble was just a missing --legacy-peer-deps somewhere. But after I wasted a ton of time earlier this week trying to migrate a gatsby starter that way and ultimately failing I instead moved this starter to the same setup as I did for https://github.com/sanity-io/sanity-template-nextjs-blog-comments

I would've loved to have time to give the docs and readme some love. But for now priority 1 was to get it functional and automated. More automation makes it more realistic we'll be able to keep it up to date.

Quick list over changes that happened to https://github.com/sanity-io/sanity-template-nextjs-blog-comments earlier today, and what's proposed to https://github.com/sanity-io/sanity-template-nextjs-landing-pages in this PR:

• Build pipeline based on environment variables all the way, working locally, the CI jobs and the deploys to Vercel.
• A CI workflow that builds both Next.js and Studio to block PRs coming in.
• A connected live deploy to the template repos, providing ever green live demos that also serves as a second line of defense should the CI fail to detect a faulty dependency update.
• The templates have two datasets. When working locally and testing PR preview links you can mess around without breaking or "uglifying" the live demos.
• Renovate is configured to use our new preset, including a brand new one for Studio v2 that silences React 18 update PRs until the Studio team gives us the go-ahead. And one for pinning our external github action workflows to commit SHA1's so bad actors can't mutate a workflow and have it do something else, like stealing our NPM_TOKEN.
• If you forget to run npx prettier --write . before you push your changes a friendly bot will fix it for you instead of giving your PR a failed check blocking you from merging.

[kmelve]

📝 Changed routes:

/[[...slug]]
(view full size)

And 1 other route:

• /api/sitemap

Commit 29f4df39c66e0dd8a3bca88aed2995f39d2b98a8 (https://template-nextjs-landing-pages-eawihiu7v.sanity.build).

[benjaminsinger]

Hi, noticed the same on this starter project. Slightly frustrating as this is pretty much the single project starter I need to get Sanity up and running for our use case.