Adds context to platform in SvelteKit endpoints (#3868)

* Added context to platform in endpoints with adapter-cloudflare.

* update docs

* Update sharp-moles-confess.md

Co-authored-by: Rich Harris <hello@rich-harris.dev>

Author: isaac-mcfadyen

.changeset/sharp-moles-confess.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+---
+
+Add `context` to `event.platform` object

packages/adapter-cloudflare/README.md

@@ -53,7 +53,7 @@ When configuring your project settings, you must use the following settings:
 
 ## Environment variables
 
-The [`env`](https://developers.cloudflare.com/workers/runtime-apis/fetch-event#parameters) object, containing KV namespaces etc, is passed to SvelteKit via the `platform` property, meaning you can access it in hooks and endpoints:
+The [`env`](https://developers.cloudflare.com/workers/runtime-apis/fetch-event#parameters) object, containing KV namespaces etc, is passed to SvelteKit via the `platform` property along with `context`, meaning you can access it in hooks and endpoints:
 
 ```diff
 // src/app.d.ts
@@ -64,6 +64,9 @@ declare namespace App {
 +		env: {
 +			COUNTER: DurableObjectNamespace;
 +		};
++		context: {
++			waitUntil(promise: Promise<any>): void;
++		}
 +	}
 
 	interface Session {}

packages/adapter-cloudflare/files/worker.js

@@ -9,8 +9,9 @@ export default {
 	/**
 	 * @param {Request} req
 	 * @param {any} env
+	 * @param {any} context
 	 */
-	async fetch(req, env) {
+	async fetch(req, env, context) {
 		const url = new URL(req.url);
 
 		// static assets
@@ -49,7 +50,7 @@ export default {
 
 		// dynamically-generated pages
 		try {
-			return await app.render(req, { platform: { env } });
+			return await app.render(req, { platform: { env, context } });
 		} catch (e) {
 			return new Response('Error rendering route: ' + (e.message || e.toString()), { status: 500 });
 		}