Experimental: add an export npm script

bin/export.js

@@ -0,0 +1,36 @@
+const fsp = require("fs").promises;
+const path = require("path");
+const puppeteer = require("puppeteer");
+
+if (process.argv.length !== 4) {
+  console.error("Usage: npm run export [url] [output-dir]");
+  process.exit(1);
+}
+
+let url = process.argv[2];
+const outputDirectory = process.argv[3];
+
+(async () => {
+  await fsp.mkdir(outputDirectory, { recursive: true });
+  const browser = await puppeteer.launch();
+  const page = await browser.newPage();
+  await page.setViewport({ width: 1920, height: 1080 });
+  let goingOn = true;
+  let slide = 1;
+  console.log(`▶️  Exporting all slides to ${outputDirectory}`);
+  await page.goto(url);
+  while (goingOn) {
+    const paddedSlide =
+      "0".repeat(2 - Math.floor(Math.log10(slide))) + slide.toString();
+    console.log(`   📸 Exporting slide ${slide}…`);
+    await page.screenshot({
+      path: path.join(outputDirectory, `slide${paddedSlide}.png`)
+    });
+    slide++;
+    await page.keyboard.press("Space");
+    goingOn = url !== page.url();
+    url = page.url();
+  }
+  await browser.close();
+  console.log("✅ Done");
+})();