F(frontend): add route loading feedback

src/lib/navigation-progress.ts

@@ -0,0 +1,35 @@
+type ProgressEvent = "start" | "done";
+type Listener = (event: ProgressEvent) => void;
+
+const listeners = new Set<Listener>();
+let active = false;
+
+function emit(event: ProgressEvent) {
+  listeners.forEach((listener) => listener(event));
+}
+
+export function subscribeNavigationProgress(listener: Listener) {
+  listeners.add(listener);
+
+  return () => {
+    listeners.delete(listener);
+  };
+}
+
+export function startNavigationProgress() {
+  if (active) {
+    return;
+  }
+
+  active = true;
+  emit("start");
+}
+
+export function completeNavigationProgress() {
+  if (!active) {
+    return;
+  }
+
+  active = false;
+  emit("done");
+}