General source code refactoring

src/content/main.js

@@ -0,0 +1,9 @@
+/** Preserve the existing document_idle initialization and observer behavior. */
+function startContentApplication({ environment, page, styles, products }) {
+  if (!page.isAllowedPage()) return;
+  styles.ensureExtensionStyles();
+  products.ensureProductsBackgroundMessageHandler();
+  if (page.insertTile()) return;
+  const observer = new environment.MutationObserver(() => page.insertTile());
+  observer.observe(environment.document.documentElement, { childList: true, subtree: true });
+}