feat(web): scrubber label and animation (#13815)

* feat(web): scrubber label and animation

* tune x fly in distance

* refactor

* lint and minor fix

* fly height

web/src/lib/stores/timeline.store.ts

@@ -0,0 +1,3 @@
+import { writable } from 'svelte/store';
+
+export const isTimelineScrolling = writable(false);