feat: add devtools updates (#673)

* feat: add devtools updates

* add comment to explain the server route

* make it an ISR route, handle errors

---------

Co-authored-by: Rich Harris <[email protected]>

apps/svelte.dev/src/routes/devtools/updates.json/+server.ts

@@ -0,0 +1,42 @@
+import { error, json } from '@sveltejs/kit';
+import type { ServerlessConfig } from '@sveltejs/adapter-vercel';
+
+export const config: ServerlessConfig = {
+	isr: {
+		expiration: 300
+	}
+};
+
+// We manage FF extension by ourselves through GH releases and this acts as `update_url`
+// for our users to automatically update their extension when a new version is released
+// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/browser_specific_settings#update_url
+export async function GET({ fetch }) {
+	const response = await fetch('https://api.github.com/repos/sveltejs/svelte-devtools/tags');
+
+	if (!response.ok) {
+		error(response.status);
+	}
+
+	const gh: Array<{ name: string }> = await response.json();
+
+	// v2.2.0 is the first version that has the Firefox extension
+	const tags = gh.reverse().slice(gh.findIndex((t) => t.name === 'v2.2.0'));
+	const base = 'https://github.com/sveltejs/svelte-devtools/releases/download';
+	return json({
+		addons: {
+			'[email protected]': {
+				updates: tags.map(({ name: tag }) => {
+					return {
+						version: tag,
+						update_link: `${base}/${tag}/svelte-devtools.xpi`,
+						applications: requirements[tag] && { gecko: requirements[tag] }
+					};
+				})
+			}
+		}
+	});
+}
+
+const requirements: Record<string, any> = {
+	'v2.2.2': { strict_min_version: '121.0' }
+};