Anonymous Polls

**Is your feature request related to a problem? Please describe.**

If you look at the hidden events for poll responses using the setting in Element, you can see who voted for what using the "answers" field in the event.:

**Describe the solution you'd like**
I'd like to suggest anonymous polls, where clients do NOT receive any event that reveals who voted for what. For even more privacy, there could also be an option to not reveal who voted in the poll at all. For these types of polls, the participating homeservers would need to keep track of the votes and only display the anonymous results to clients.

**Describe alternatives you've considered**
There is currently no alternative to completely hide what you voted for on a Matrix poll. Element does not currently show who voted for what on the actual poll UI as mentioned in #533 (see "non-anonymous polls"), but despite this the events are all still available to users who know where to look (e.g. hidden events).