Add screenshot capture functionality

app/screenshots/HttpServer.mjs

@@ -0,0 +1,32 @@
+import http from 'http';
+import ecstatic from 'ecstatic';
+
+export default class HttpServer
+{
+  /** @var {http.Server} */
+  #server = null;
+
+  get port() {
+    return this.#server.address().port;
+  }
+
+  start() {
+    return new Promise((resolve, reject) => {
+      if (this.#server) {
+        return resolve();
+      }
+
+      const handler = ecstatic({ root: './dist' });
+      this.#server = http.createServer(handler);
+      this.#server.on('listening', () => resolve());
+      this.#server.listen();
+    });
+  }
+
+  async stop() {
+    if (this.#server) {
+      await this.#server.close();
+      this.#server = null;
+    }
+  }
+}

app/screenshots/captureScreenshot.mjs

@@ -0,0 +1,44 @@
+import { URL } from 'url';
+import puppeteer from 'puppeteer';
+import HttpServer from './HttpServer.mjs';
+
+const defaultViewport = {
+    // Using a 16:9 ratio here by default to match Twitter's image card dimensions
+    width: 1200,
+    height: 675,
+    deviceScaleFactor: 2,
+};
+
+export async function captureScreenshot(path, options = {}) {
+  const httpServer = new HttpServer;
+  await httpServer.start();
+
+  // Launch a new Chrome instance
+  const browser = await puppeteer.launch({
+    args: [
+      '--no-sandbox', // Allow running as root inside the Docker container
+    ],
+    // headless: false, // For testing
+  });
+
+  // Create a new page and set the viewport
+  const page = await browser.newPage();
+  const viewport = { ...defaultViewport, ...options.viewport };
+  await page.setViewport(viewport);
+
+  // Navigate to the URL
+  let url = new URL(`http://localhost:${httpServer.port}/screenshots/`);
+  url.hash = path;
+  await page.goto(url, {
+      waitUntil: 'networkidle0', // Wait until the network is idle
+  });
+
+  // Take the screenshot
+  let result = await page.screenshot();
+
+  // Close the browser and HTTP server
+  await browser.close();
+  await httpServer.stop();
+
+  return result;
+}