refactor: share dom ready

static/utils.ts

@@ -11,3 +11,12 @@ export const parseClassList = (value: string | null): string[] => {
     .map((entry: string): string => entry.trim())
     .filter((entry: string): boolean => entry.length > 0);
 };
+
+export const onReady = (fn: () => void): void => {
+  if (document.readyState === "loading") {
+    document.addEventListener("DOMContentLoaded", fn, { once: true });
+    return;
+  }
+
+  fn();
+};