Keep cached cycles active in background tabs

cycle-worker.js

@@ -0,0 +1,11 @@
+const INTERVAL_MS = 60000;
+
+postMessage({ type: "ready", at: Date.now() });
+
+self.onmessage = event => {
+  if(event.data && event.data.type === "ping") postMessage({ type: "ready", at: Date.now() });
+};
+
+setInterval(() => {
+  postMessage({ type: "cycle", at: Date.now() });
+}, INTERVAL_MS);