Add experimental prerenderWorker option

[jamesopstad]

Adds an experimental prerenderWorker option for defining a dedicated Worker for pre-rendering.

Example:

cloudflare({
  experimental: {
    prerenderWorker: {
      config(_, { entryWorkerConfig }) {
        return {
          ...entryWorkerConfig,
          name: "prerender",
          main: "./src/prerender.ts",
        };
      },
    },
  },
}),

Internally, the plugin now sets an environment variable during the build that indicates to the preview server that the prerender Worker should be used as the entry. This means that the Vite preview server can be used during the build to send requests to the prerender Worker.

An example of usage is included in https://github.com/cloudflare/workers-sdk/blob/803348985820e61a7e11a554a5633a8cadbe3751/packages/vite-plugin-cloudflare/playground/prerendering/vite.config.ts.

---

• Tests
  • Tests included/updated
  • Tests not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: experimental and should be undocumented for now
• Wrangler V3 Backport
  • Wrangler PR:
  • Not necessary because: not a Wrangler change

A picture of a cute animal (not mandatory, but encouraged)

[changeset-bot]

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Latest commit: 8033489

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commit: 8033489

[matthewp]

We have this working in withastro/astro#15077

This change works for us.