Toggle hidden content visible for visual regression tests (#160)

* Toggle hidden content visible for visual regression tests

**Why**: Check for regressions of content which may be collapsed (hidden) by default.

* Apply lint fixes

test/screenshot.test.js

@@ -38,9 +38,15 @@ async function stubAnimations() {
   });
 }
 
+async function toggleHiddenContent() {
+  await page.$$eval('.usa-accordion__container', (containers) =>
+    containers.forEach((container) => container.removeAttribute('hidden')),
+  );
+}
+
 async function getScreenshot(url) {
   await page.goto(url);
-  await stubAnimations();
+  await Promise.all([stubAnimations(), toggleHiddenContent()]);
   return page.screenshot({ fullPage: true });
 }