Fix polyfills not being available to imports on Netlify (#6117)

* fix(netlify): Try to make polyfill external

* feat(webapi): Add polyfill applier for SSR

* fix(netlify): Externalize polyfills so they're always applied before user code

* chore: changeset

* test(netlify): Add test for polyfill being in the proper place

* config(netlify): Remove unnecessary change to package.json

* revert(netlify): Revert changes

* feat(astro): Add a way for packages to explicitely mark themselves as needing to be external

* Update .changeset/silent-dragons-sell.md

---------

Co-authored-by: Nate Moore <natemoo-re@users.noreply.github.com>

.changeset/silent-dragons-sell.md

@@ -0,0 +1,6 @@
+---
+'@astrojs/netlify': patch
+'astro': patch
+---
+
+Fix polyfills not being available in certain cases

packages/astro/src/core/create-vite.ts

@@ -55,6 +55,12 @@ export async function createVite(
 		isBuild: mode === 'build',
 		viteUserConfig: settings.config.vite,
 		isFrameworkPkgByJson(pkgJson) {
+			// Certain packages will trigger the checks below, but need to be external. A common example are SSR adapters
+			// for node-based platforms, as we need to control the order of the import paths to make sure polyfills are applied in time.
+			if (pkgJson?.astro?.external === true) {
+				return false;
+			}
+
 			return (
 				// Attempt: package relies on `astro`. ✅ Definitely an Astro package
 				pkgJson.peerDependencies?.astro ||

packages/integrations/netlify/package.json

@@ -50,5 +50,8 @@
     "cheerio": "^1.0.0-rc.11",
     "mocha": "^9.2.2",
     "vite": "^4.0.3"
+  },
+  "astro": {
+    "external": true
   }
 }