Adds a prefetch integration for near-instant page navigations (#3725)

* Adds a basic @astrojs/prefetch integration

* adding tests for custom selectors

* missed in last commit

* Adding a few docs, removing the option for `selectors` to be an element array

* adding an option for the concurrency limit

* fixing test for updated integration options

* Update packages/labs/prefetch/src/client.ts

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

* nit: removing the NodeJS.Timer type to allow typescript to infer the return

* updating docs for default selector with ~=

* Skip prefetching on 2G connections, or when data saver is enabled

* refactor: moving to packages/integrations, Astro Labs TBD down the road

* README typo fix

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

1 files changed, 17 insertions, 0 deletions

diff --git a/packages/integrations/prefetch/src/index.ts b/packages/integrations/prefetch/src/index.ts
new file mode 100644
index 000000000..15f52272c
--- /dev/null
+++ b/packages/integrations/prefetch/src/index.ts
@@ -0,0 +1,17 @@
+import type { AstroIntegration } from 'astro';
+import type { PrefetchOptions } from './client.js';
+
+export default function (options: PrefetchOptions = {}): AstroIntegration {
+	return {
+		name: '@astrojs/lit',
+		hooks: {
+			'astro:config:setup': ({ updateConfig, addRenderer, injectScript }) => {
+				// Inject the necessary polyfills on every page (inlined for speed).
+				injectScript(
+					'page',
+					`import prefetch from "@astrojs/prefetch/client.js"; prefetch(${JSON.stringify(options)});`
+				);
+			}
+		}
+	};
+}