Add to-do items websocket subscription for to-do widget

**Is your feature request related to a problem? Please describe.**
When to-do items are renamed or reordered the change will not be picket up by to-do widget as currently we relay on entity change events and for those operations entity will not change the state.

**Describe the solution you'd like**
Add new websocket subscription that will trigger changes if anything in to-do list is changed.
https://github.com/home-assistant/core/blob/dev/homeassistant/components/todo/__init__.py#L322

**Describe alternatives you've considered, if any**
N/A

**Additional context**
https://github.com/home-assistant/android/pull/5169#pullrequestreview-2769166656