Add 'infinite' gallery support.

src/utils/basic.ts

@@ -155,3 +155,11 @@ export function getDurationString(start: Date, end: Date): string {
   duration += `${seconds}s`;
   return duration;
 }
+
+/**
+ * For debug purposes only.
+ * @param seconds 
+ */
+export const sleep = async (seconds: number) => {
+  await new Promise(r => setTimeout(r, seconds * 1000));
+}