fix(vercel): update middleware esbuild settings

[ascorbic]

Changes

Vercel builds its own edge functions with the esnext target, because the Cloudflare workerd runtime they use updates v8 every week.

See comment here

Also updates conditions slightly so that it also includes the workerd condition. Browser doesn't need to be manually added as it's included by default

Fixes #495

Testing

Added top level await to a edge middleware to ensure it works. It won't compile with the previous settings.

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: e5b6158

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 20 packages

Name	Type
@astrojs/vercel	Patch
@test/astro-vercel-basic	Patch
@test/astro-vercel-image	Patch
@test/astro-vercel-integration-assets	Patch
@test/vercel-isr	Patch
@test/vercel-max-duration	Patch
@test/vercel-edge-middleware-with-edge-file	Patch
@test/vercel-edge-middleware-without-edge-file	Patch
@test/astro-vercel-no-output	Patch
@test/astro-vercel-prerendered-error-pages	Patch
@test/astro-vercel-redirects-serverless	Patch
@test/astro-vercel-redirects	Patch
@test/vercel-server-islands	Patch
@test/astro-vercel-serverless-prerender	Patch
@test/astro-vercel-serverless-with-dynamic-routes	Patch
@test/astro-vercel-static-assets	Patch
@test/astro-vercel-static	Patch
@test/vercel-streaming	Patch
@test/astro-vercel-with-web-analytics-enabled-output-as-static	Patch
vercel-hosted-astro-project	Patch

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